There are many ways to import books into the app, most initiated from the multi-tabbed Exchange View. In general, you can either import books by downloading from websites, or from your computers. Websites cover OPDS and HTML websites, including cloud services such as Dropbox. Otherwise, you can use Finder/iTunes/Files, AirDrop, Calibre (Wi-Fi) or our PC Upload (Wi-Fi) service. Unless you have a strong personal preference, we recommend using PC Upload.
* Note that for all ways to import from your local computer, we assume that your iOS device and the computer are on the same local area network. If your iOS device has a cellular data connection in addition to a Wi-Fi connection, make sure that the Wi-Fi connection is the preferred connection. (In case you are not sure about it, you may turn off the cellular data connection.) Moreover, you may verify that there is a good connection between your iOS device and your computer server by trying to access the server by entering its IP address with port number into a web browser (such as Safari) on your iOS device. If there is no good connection, rebooting your router may help. Finally, make sure that the app has been granted access to your local network. In Settings app, go to Privacy & Security > Local Network > MapleRead, and turn on the switch.

Go to Exchange | Files view.   The answer depends on which tool you are using.

1. Finder for macOS 10.15 Catalina or later: After you have copied the files to this device by Apple's standard method❶, tap the Action button and select Import.
2. iTunes app for macOS 10.14 Mojave or earlier or Windows: After you have copied the files to this device by Apple's standard method❷, tap the Action button and select Import.
3. Files app for iOS: Open Files app on your iOS device to copy files or folders to “MapleRead SE (CE/CX)” under “On My iPad (iPhone)” by Apple's standard method❸, then tap the Action button and select Import.

❶ https://support.apple.com/en-us/HT210598
❷ https://support.apple.com/en-us/HT201301
❸ https://support.apple.com/guide/iphone/organize-files-and-folders-iphab82e0798/ios
For your convenience, similar information is also available inside the app when the Files view is empty.   If and only if the view is non-empty, Import will be enabled.   Tap Import, and then a simple confirmation dialog will be shown.  

Advanced Usage: If you have used Files app to copy one or more folders into MapleRead's folder here, for the convenience of some of you (who are not confused yet) you may optionally choose to infer the parent folder names as book set names, if you turn on Infer Book Set during Import via Exchange | Files.   Tap Import, and then a not-so-simple confirmation dialog will be shown.  

PC Upload allows you to easily upload files to MapleRead from your PC using a web browser without installing any plugin or software program.

1. app: Go to the PC Upload View, which is one of the Exchange views reachable from the Library View by tapping the exchange button at the upper left corner, and tap Start  
2. PC: Open a modern web browser and type in the URL as instructed by the app
3. PC: Click the Select Files button to select one or multiple files at a time. Alternatively, drag and drop one or multiple files at a time from any desktop folder to the Drop Files Here area.   
4. app: Monitor the import status of each file as it is transferred and processed   

Note that you may connect to the app this way from multiple computers at the same time.

If you know how to select multiple book entries (files) in Calibre Library View and then drag-and-drop them to the desktop, then you may apply the same method to drag-and-drop them to the Drop Files Here area of the browser window    as explained in “How to import books via PC Upload?”

Start Calibre's Content Server on your PC, and connect to the server from the app, then download books as usual as from any OPDS server.

1. calibre: Click the Connect/share button, then select Start Content Server in the drop-down menu  
2. calibre: Verify that the server is really up by clicking the Connect/share button again and confirming that Stop Content Server is displayed in the drop-down menu  
3. app: Go to the Websites View  , which is one of the Exchange views reachable from the Library View by tapping the exchange button at the upper left corner
4. app: Make sure that OPDS segment on the top is highlighted. Tap Edit, and then tap Scan for OPDS sites via Bonjour on the same local area network  , where Bonjour is typically bundled with iTunes. (Please verify that the app has been granted access to your local network. In Settings app, go to Privacy > Local Network > MapleRead, and turn on the switch.)
5. app: Within a few seconds, the Calibre server should be discovered  . If yes, go to Step 9.
6. app: However, if somehow the server is still not discovered, even after repeating Step 4, then add it manually.
7. calibre: Find out the server URL, which is displayed after the term Stop Content Server  
8. app: Tap Add OPDS site, and enter the server URL followed by /opds as the OPDS Catalog Address, then tap Save  
9. app: Tap Done to exit Edit mode. Download books as usual from any (built-in or user-defined) OPDS server, including the use of Smart Batch Download
10. app: If the server or website is password protected, you will be prompted to login. You may choose to save your credentials locally for convenience.

By default, Calibre's Content Server returns a maximum of 30 OPDS items per query. If you have hundreds or even thousands of books there and want Calibre to return the full book list with just one instead of tens or even hundreds of queries, you need to change that maximum number.

1. From the top menu, open Preferences > Preferences  
2. In the Preferenes dialog, open Sharing over the net  
3. In the Sharing over the net dialog, change the value of Max. OPDS items per query from 30 to a number larger than the number of books stored there, and click Apply  
4. Click the Stop Server button if applicable
5. Follow the instructions of “How to import books from Calibre?” as needed

Instead of downloading books one at a time, with Smart Batch Download you may download many books in a batch with only a few taps from any OPDS catalog. Let's use a built-in OPDS catalog as an example.

1. Go to Exchange's Websites (OPDS) view and tap Samples (Books & More) | Sample Books
2. On the top toolbar tap the icon ⬇️    to enter Smart Batch Download mode
3. On the top toolbar with the new icons on the right, tap All  
4. Tap the third icon from the left to initiate the actual background downloading of all selected book files

Instead of or in addition to Step 3, you may tap any row entry to select or de-select it for download.
Actually Smart Batch Download is much more powerful than just described. Let's look at each of its Prefer menu sections.    

• When multiple formats are available: you may prefer to download one or more formats of the same book entry where applicable.
• For EPUB, if OPDS and embedded metadata differ: you may prefer one over the other. Note that Prefer OPDS over Embedded is the implicit default choice in other context. (For a self-help demo, go to Exchange view. Navigate to Websites (OPDS) | Samples (Books & More) | Sample Books 2.
• If Library has the same title and author(s): you may choose Skip Book (which won't waste time re-downloading the same book if it is indeed the same, but will miss downloading a different book otherwise), or Download Book (which will always download the book), or Overwrite Metadata (which will download only the typically tiny metadata), or Overwrite Library Book (which will be useful for updating serial-story books). The default is Skip Book, as avoiding unnecessary time-consuming re-downloading is typically the most preferred choice.
• If the downloaded book is a duplicate: you may choose Keep Metadata or Overwrite Metadata.

Note that book title and author(s) are part of the book metadata. If you later update the title and/or author(s) of a given book in Calibre, then obviously you can no longer rely on the assumption that the OPDS copy and the Library copy share the same title and author(s). In this case, you need to choose Overwrite Metadata for If the downloaded book is a duplicate. Otherwise, choosing Overwrite Metadata for If Library has the same title and author(s) should be sufficient for updating the metadata. Moreover, if you want to add or update series of a book from calibre after you have downloaded the book to the app, you may do so by choosing Overwrite Metadata. In all cases, we recommend that you have disabled the relevant metadata writer plugins of Calibre.

Let's use Dropbox and MapleRead SE as our example. There are multiple ways to import files from Dropbox. We think the best way is to leverage Apple's Files app (available for iOS 11 and later) to copy files or folders from one app to another (our app in this case), followed by tapping Import inside MapleRead SE. Note that the exact sequence of doing copy and paste inside Files is subject to change by Apple.

• Open Dropbox app on your iOS device, and sign in.
• Open Files app. Check if Dropbox is listed under Locations in its menu. If not, tap ⋯ at the upper right corner of the menu, followed by Edit, then turn on Dropbox, and tap Done.
• Inside Files app, tap Dropbox to enter Dropbox view. Stay at the top level or go to a lower level directory you want to import from. Tap Select and then the item(s) you want to import. Long press on the item and select Copy. This may take a while if you are copying a lot of files.
• Inside Files app, tap Browse tab to go back to the top level, open Locations | On My iPad (iPhone) | MapleRead SE. Long press and select Paste. Verify that copying is done.
• Open MapleRead SE. Go to Exchange | Files view, which shows all potentially importable top-level files and directories. Tap the action menu and tap Import. See also Advanced Usage of Import via Files

Note that it works similarly for other cloud drive services, such as iCloud Drive, Google Drive, and Microsoft OneDrive, once you have installed and signed in the apps, for any edition of MapleRead SE/CE/CX.
We recommend you to try out this import method first with a few books in order to gain a solid understanding, before importing all your books in one shot.

Yes, you may change the default import destination book set. First, open Switch Book Set popup.   Tap the “download tray” icon, and note that the title has changed to Pick Import Destination.   Tap another book set, say, “Standard Ebooks”, and note that the icon has moved there.   Finally, tap Done, and read the reminder message.   Tap OK to proceed, and note the title has changed back to Switch Book Set.  
Caveat: If you switch to another book set later, you may have a hard time finding the books just downloaded, because they were downloaded into a book set not currently visible to you! Remember to switch to the import destination book set, or All Books, and sort by Date Added.

Books published in neither EPUB nor PDF but in one of over a dozen other formats such as MOBI, AZW3, FB2, TXT can be easily converted by Calibre into EPUB, the most common open ebook format. The converted EPUB books can then be imported from Calibre. Don't worry too much about the technical details in Calibre's ebook conversion manual. The default setting is usually good enough for an excellent conversion result.

Digital rights management (DRM) schemes are access control technologies. There are a few major competing DRM schemes for e-books, including the ones from Adobe, Amazon and Apple respectively. If you own a non-DRM-free book and want to read it with another ebook reader which takes only DRM-free books, then the DRM stuff must first be removed with some deDRM tool. After the book is deDRMed, it can then be converted with Calibre to EPUB as needed. Purchasing DRM-free ebooks in the first place is perhaps a better option if they are available.

The iOS Kindle app does not have the capability to export its books to another app on the same device. However, you can access the book files by downloading or syncing them to your PC or Mac using “Kindle for PC” or “Kindle for Mac”. The book files are all stored in Content Folder, the location of which can be found by opening Kindle's Preferences View. Once the book files (with extension azw, azw3, or mobi) are located, they may be deDRMed and converted as needed, before importing.

Open a (EPUB) book, tap the middle of the screen to bring up the top toolbar, then tap the button to bring up the Theme Control View. Tap Edit Theme to bring up another popup view. Tap a (user-defined) theme entry to bring up the Theme Settings View.    Tap Export... and choose one of the three ways to export & share.

In the Library Bookshelf View, tap Scenes button to bring up the Scene Control View. Tap Edit Scene to bring up another popup view. Tap a (user-defined) scene entry to bring up the Scene Settings View. Tap Export... and choose one of the three ways to export & share.

There are two methods to share books in the library: (1) sharing by selected book sets, and (2) sharing by selected books. For the first method, go to Server View, select OPDS or HTML in the top segment control, and follow the instruction there.   For the second method, go to Library View first. To select one book to share, long press on a book and then tap Server.    To select multiple books to share, tap Edit, select multiple books and tap the action button at the upper-left and then tap Server.
If you want MapleRead SE (the server), say on an iPad, to serve another MapleRead app (the client), say on an iPhone, then the client should just follow the instructions marked for app in the answer to How to import books from Calibre via its Content Server?
If you also want to share a book's metadata and set membership, then you must use the OPDS server. Suppose you want to share all EPUB books on the server. On the server side, make sure All Books is selected before tapping Start. On the client side, select All Books. Then select By Format, and EPUB.    Tap ⬇️ to enter Smart Batch Download mode. Tap Prefer, and select both Overwrite Metadata and Clone Set Membership.    Select some or all the books and then tap the download button.

PC Upload allows you to easily install user fonts to MapleRead from your PC using a web browser without installing any plugin or software program.

1. app: Go to the PC Upload View, which is one of the Exchange views reachable from the Library View by tapping the exchange button at the upper left corner, and tap Start  
2. PC: Open a modern web browser and type in the URL as instructed by the app
3. PC: Click the hyperlink Go to Font Installer on the right below the big icon.    
4. PC: Click the Font Files button to select one or multiple font files (.ttf, .ttc, .otf) with the same embedded font family name in one shot (on Mac OS X or Windows). Alternatively, select just one .zip file containing such font files.  
5. PC: Enter the optional Font Display Name. If set, this name instead of the embedded font family name will be used for display purposes in Text Font and Heading Font menus of MapleRead. While the embedded name is typically encoded in ASCII, the display name provided by MapleRead is encoded in Unicode, which is great for showing non-English European names, Chinese/Japanese/Korean names and names in other languages of the world.   Just leave it blank if you don't have a good reason not to do so. (You will then know the embedded font family name after a successful installation.)
6. PC: Click the Install button.
7. app: Monitor the import status of each attempted font installation as the files are transferred and processed   
8. PC: Go to Step 4 to install another font.

From the Text Font menu of any EPUB book, simply swipe left to delete the user font entry you want to uninstall, one at a time.   You may also uninstall all user fonts in one shot by turning on Remove All User Fonts in iOS System Settings, followed by an app restart.  

No, not directly. But you can first uninstall the user font, then install it again with a new font display name.

No. If the installed font is a user font (instead of a built-in font), you can first uninstall the user font, then install it again with all the relevant font files of the same font family in one shot.

A typical EPUB book makes use of four font styles, namely, regular, bold, italic, and bold italic. Therefore, you are recommended to install those four styles for each user font all at once.   (It doesn't hurt to install other styles of the same font, but probably you won't gain anything more, unless you know your book can take advantage of them by design.) However, for Chinese/Japanese/Korean books written in Han characters, only one style (regular style) for each font is typically supplied by the font foundries.  

In a top-level Library view, tap Sort and select Date Read, you will then see all the books listed in reverse chronological order with your most recently read book on the top. This always works unless you have switched the current book set since you close the book. In that case, switch to the built-in book set All Books, and you'll definitely see the book on the top.

In any library view, do Sort by Date Read. As the sort is in reverse chronological order, scroll to the bottom for your unread books under the Never Read section. To show only classic/romance/science fiction or books of other subjects, tap Tags to open up a menu, and tap None, followed by selecting one or more matching tags of your interest. The more tags you select, the more matching books you'll find. Note that a book may have zero or more associated tags.

In any library view, long press on the book to open a menu, then tap Get Info to open the Metadata view. Alternatively, you can open the view by just tapping on the book icon in any book-list view. Tap Edit on the upper-right hand corner to enter Edit mode. You may now edit any part of the metadata, and the cover image by tapping the corresponding button.  

A book set is a collection of books. Every book in the Library can be in one or more book sets. The special set All Books contains every book stored in the Library. You can create a book set with a name you pick, such as “My Favorites” or “Reading List”, to group the books you choose. You can create as many such user-defined book sets as you wish.
A book that does not belong to any user-defined book set is automatically placed in another special set Ungrouped. Thus it is often convenient to switch to Ungrouped, and start to organize books by moving them from there to some user-defined book sets.

You may create an unlimited of user-defined book sets, where each book set can contain any number of books you want. Note that a book can be in one or more book sets at the same time. To create a user-defined book set,

1. Start from any Library view, and tap near the upper right corner
2. Tap Edit in the popup titled Switch Book Set
3. Tap the first table row with the label New Book Set...
4. Enter the name of this book set as chosen by you and tap OK
5. Tap Done

You may move or copy one or more books at a time from one book set A to another book set B as follows. Suppose the library is set in flat list view.

1. Tap and switch to book set A if needed.
2. Tap . There is now a circle on the left of each row.
3. Tap each book that you want to move (copy). Scroll the view if needed.
4. Tap Move (Copy) at the bottom, and then choose book set B in the popup menu.
5. Tap ╳ at the upper left corner when done moving (copying).

Note that if A is All Books, which by definition contains all books, you can only copy but not move from A.

Suppose the library is set in a flat view.

1. Tap and switch to the book set if needed.
2. Tap . There is now a circle on the left of each row.
3. Tap each book that you want to delete. Scroll the view if needed.
4. Tap
5. Tap ╳ at the upper left corner when done deleting.

You may sort books in any (custom) order you like in each user-defined book set created by you, but not in the two built-in book sets, namely All Books and Ungrouped. As each user-defined book set has its own custom order, changing the custom order of one set does not affect that of another set. Now, assume that you have switched to a user-defined book set, say, “Demo”, and want to re-order its books as you like.

1. Switch to the Flat Booklist view
2. Change Sort type to Custom Order  
3. Tap (Edit)
4. Tap Reorder  
5. Long press and drag each book to where you like  
6. Tap ╳ when done

You may then switch to the Flat Bookshelf view if you like. Note that the custom ordering of books in the Flat Booklist view (going top-down) and that of the Flat Bookshelf view (going top-down left-right) are the same. Note that the same custom ordering is used in both portrait and landscape orientations.

A tag may be used to denote a category, a subject or any attribute you deem appropriate. A book may have zero, one or more tags. For each book set, there is a corresponding tag list   , which is shown on tapping Tags in a library view. The tag list contains and only contains all tags of every book in the set, plus the special tag [Untagged] in case some book does not have any tag.
A book of a set is visible if and only if it has at least one tag matching a checked tag in the corresponding tag list.    Note that by checking and unchecking tags, you only affect the visibility of the books, but not their actual set membership.

The tag pool of your library    is the set of all tags ever assigned to any one book of your library, plus optional tags you have explicitly added. It is accessible by tapping Tags and then Pool. To add a new tag to the tag pool, you may enter it by typing, or tapping + to access a list of category tags    commonly found in bookstores and physical libraries.

Go to a Library view.

1. Tap
2. Tap each book that you want to assign (unassign) the same tags
3. Tap the action button at the upper left corner, and then choose Assign Tags...   in the popup menu
4. Select segment ⊕, and select each tag you want to assign
5. Select segment ⊖, and select each tag you want to unassign
6. Tap Save  

Note that book tag assignment and unassignment performed inside the app are saved as app data, and do not modify the book files themselves (and thus their unique MD5 signatures).

Yes. EPUB books usually embed multiple subject attributes, which are extracted and saved as tags after import in general. However, if they are imported via OPDS catalogs, then the tags of the corresponding OPDS entries completely override the embedded ones.

As any book in this app's library may have multiple tags, and may belong to multiple book sets, you may organize your library by purely using tags or sets. There is no single correct way to organize. However, we recommend you to use a hybrid organization. Use tags for intrinsic attributes such as Biography, History, Science, Romance, Science Fiction, and Thriller; use sets for extrinsic attributes such as My Reading List, and My Favorites.

First, make sure that your book does have non-empty series and volume. Open Book Info view. If present, they should be displayed right under the book title.   If absent, they may be restored in Edit mode by tapping Series (Volume) | Restore from Book.  
Assume for now that there are non-empty series and volume. Then they are always displayed in the Flat Booklist view, no matter how the library is sorted, as long as Abridge Info    is turned off, and Prefer Date Details    is also turned off.

Turn on Diagnostics in System Settings   . The next time you do a pinch-and-spread    for font size change, you'll see the current reading font size.

This is because the text (heading) color of each theme can only be set to one color for all text. However, you may choose not to override publisher's colors in Apply Theme Colors. See figure   for details.

First, try not to override colors in Apply Theme Colors. If this is not good enough, you may create your own theme(s), with colors you like. Start by tapping Edit Theme | New Theme… to open Theme Editor  , which is initialized as a clone of the current theme.

From within an EPUB book, tap the middle of the screen to bring up the top toolbar. Tap the third icon from the left to bring up a popover view and select the VOCAB segment. Swipe to left on the vocab item you want to delete and tap the red Delete button to confirm. Note that this is a standard iOS swipe gesture that can be found in many iOS apps.

To choose a different dictionary for Define, follow the following steps: (1) open an EPUB book, (2) select some text so as to bring up the context menu, (3) tap More to bring up the More menu, (4) in the Dictionary for Define section choose something else other than the default, iOS Dictionary.
If you choose My Dictionary, you may further customize it by tapping Set My Dictionary... to enter the dictionary URL. A good example of such URL is http://en.wiktionary.org/wiki/{text}, where {text} stands for the word or string to be looked up. Another example is https://en.wiktionary.org/wiki/{text}. In these two examples, http and https are the respective URL schemes.
An iOS dictionary app may or may not have a correpsonding URL scheme. If it has one and you know it, you may use it for My Dictionary. For example, the URL scheme for the iOS dictionary app “Eudic” is eudic://dict/{text}.
Even if the proper URL that should embed “{text}” is missing or unknown, it is still useful. For example, the URL scheme (or one of the URL schemes) of “Merriam-Webster Dictionary” app is “mw-collegiate”, but its proper URL is unknown. To work around the syntax check, enter mw-collegiate://{text}. The catch is that you will then have to manually paste the text into some search bar of the dictionary app when opened. Remember to turn on Implicit Copy in the More menu, so that the selected text is automatically copied to the shared system pasteboard as a side effect of executing such command.

To set up your own custom command, follow the following steps: (1) open an EPUB book, (2) select some text so as to bring up the context menu, (3) tap More to bring up the More menu, (4) turn on Show My Command, (5) tap Set My Command... to enter your own command name, and the URL. A good example of such URL is comgooglemaps://?q={text}, where {text} presumably stands for the place name to be looked up in “Google Maps” app. In cases where you only know the URL scheme but not the proper URL, consult the answer to How to choose a different dictionary? for a workaround.

Yes, when the URL scheme in question is either http or https. Two web browser apps are supported. To specify “Safari” app, prepend “{safari}” to the URL. To specify “Google Chrome” app, prepend “{chrome}” to the URL. For example, {safari}https://en.wiktionary.org/wiki/{text} will always open the URL with Safari instead of the built-in simple web browser for Define. This may be useful if you prefer the full-screen view of Safari. Note that this prefix convention is an advanced feature of MapleRead and is not a universal standard.

Open Settings app. Turn on Accessibility | Spoken Content | Speak Selection. Optionally change settings of Highlight Content, Voices and Speaking Rate as you wish. Also make sure to turn off Suppress Speak in the EPUB context “more” (...) menu.   The Speak command should now be visible.  

Open the book containing the notes of interest, tap the middle of the screen to bring up the top toolbar, then tap the button to bring up a multi-segment view. Select the NOTES segment to see the Note List View.
If you want to choose another note list as This List, tap the label in the middle of the third row for iPad, or tap the button on the left of the second row for iPhone.

In the Note List View, tap the button, and select Book Location.  

In the Note List View, tap Edit, then select at least one note. Tap the now-enabled button, and choose one of the three ways to export & share.  
Note that the exported format is for importing to (another instance of) the app later. If you want to read your notes outside the app, see here.

Yes. One way is for each of you to switch to your own note list when you read. Note that you can create and name as many note lists as you like.

You can view your notes and vocab via a web browser running on a PC, Mac or (iOS or Android) mobile devices, after the data have been synced to the Cloud. To view the sync data securely, go to www.maplepop.com and click Login in the top menu bar, and then follow the instruction there. Once you can view your sync data, you can view the updated data (due to your latest sync from your iOS device) by refreshing the corresponding webpage. Since your notes and vocab are now presented in HTML, you may easily save them as files, or copy any part of them and paste them elsewhere as you wish.

Absolutely no. Two books are considered identical by MapleRead if and only if the two corresponding book files are bit-by-bit identical. Note that two books with identical metadata (title, author, series, tags) and/or filenames are not necessarily identical. If you suspect that two books in MapleRead's library are duplicates, you may reassure yourself that they are not by verifying that they have different MD5 values. To find out a book's MD5 value, which is computed by MapleRead when the book is added, turn on Diagnostics in System Settings   , and then look at the last line in the corresponding Book Info View.

You need to create a Maplepop account if and only if you want to take advantage of our Secure Sync feature. You don't need it for anything else. Note that your Maplepop ID doesn't have to be the same as your Apple ID. Each ID should have its own password anyway.

In any Library view, tap the leftmost icon of the top toolbar. Sign out first if already signed in. Tap Sign In to bring up the Maplepop Account view.   Tap Help of that view, and then follow the instruction in the resultant view.

Suppose you want to sync data of a book from device A to device B.

1. device A: Open the book, bring up the toolbar, tap the button.
2. device B: Open the same book, bring up the toolbar, tap the button.

Note that for device A to see the data changes by device B that has now synced to the Cloud, device A should sync again from the Cloud.
If you want to sync the whole library at a time, you can easily do that by simply tapping the button near the bottom of the Library View. If you want to sync data for multiple books at a time, you can do that by tapping Edit, then tapping each book you choose to sync, and tap the action button (at the upper left corner) and tap Sync.
Please note that the book itself is not synced, only its data (reading position, notes, vocab and bookmarks) is synced.

Suppose your network connection is fine for both devices A and B. The most likely reason of failure is that the supposedly identical book on device B is actually different from the one on device A. This can be checked by comparing the MD5 values, as explained in “Does MapleRead ever allow duplicated books in its library?”

If you have somehow updated the metadata of the book in Calibre between the two download events, and you import via Calibre's Content Server, then the two downloaded (EPUB) book files can be different due to the change in metadata. By default, Calibre generates a new book file on-the-fly by modifying the original book file with its current metadata as saved in Calibre's Content Library. In contrast, if you drag-and-drop the book from Calibre to PC Upload, then what is downloaded is always the original book file. However, you can change the default behavior of Calibre's Content Server to always serve the original book files by disabling some plugin. Open Preferences > Plugins. Select Metadata writer plugins > Set EPUB metadata, and disable it by pressing Enable/Disable plugin. Disable similar plugins for books of other file formats as needed.
It turns out that there is another case in Calibre 3.x and 4.x, where a mere opening of a book with Calibre's built-in ebook-viewer may modify the original book file by adding annotations/bookmarks. To disable this default Miscellaneous option, turn off Keep a copy of bookmarks/current page inside the e-book file, for easy sharing, or Keep a copy of annotations/bookmarks in the e-book file, for easy sharing in Calibre's 3.x or 4.x E-book viewer configuration respectively.
Finally, remember to restart the Content Server.

Verify that the sync data is still sitting safely on the Cloud as expected. Import exactly the same book again, open the book and then tap the button.

Yes. In iOS System Settings. find the matching app name entry, turn on Restore Built-in Books, followed by an app restart.

Yes. Go to the Exchange Files tab and tap the action menu  

• Tap Help to read about file transfer via iTunes or Files
• To backup, tap Backup, and follow the instruction there.
• To restore, tap Restore, and follow the instruction there.

If your device, say iPhone, has enough room, making use of Files would be best. When you do backup on MapleRead CE, copy the backup folder from On My iPhone | MapleRead CE to On My iPhone | MapleRead SE, and complete backup. Thereafter, do restore on MapleRead SE.

Suppose you want to copy from device A to device B. Do a backup on device A, and then do a restore on device B. If you use iTunes to store a copy of the backup folder, then your computer can be used to transfer the folder from one device to another. If you use Files, you may use your cloud drive to do the transfer.

If your app used to work before the update, there is a chance that the updated app from App Store is somehow corrupted, and thus a reinstalled app will work. But don't delete the app, as you will lose the app's data. Instead offload the app and then reinstall it. To offload any app, use iOS Settings. Inside General | iPhone (iPad) Storage, scroll down to the app you want, tap on it and select Offload App. After the app is offloaded, select Reinstall App to reinstall it.

You may look at Overview and What's New, especially the screenshots there. In case you've missed the in-app Help   reachable from the main menu   of any Library view, please take a good look at it anyway.

In order to fix the bug, we need to reproduce the bug first. If you can reproduce the bug with our bundled book Alice's Adventures in Wonderland, or any book that can be downloaded from Samples (Books & More), then tell us which book to test. Otherwise, please send us the book with the following easy steps:

• Long press on the book in Library view
• Select Report Bugs…
• Fill in the bug description