Apple provides a way for you to back up your iBooks on iCloud. This can be done automatically or on demand.
To back up your iBooks automatically, go to Settings iCloudStorage Manage Storage. Under Backups, turn on iCloudBackup.
To back up your iBooks on demand, open iBooks and tap the Bookstore tab. Tap iCloudBackup in the upper-left corner of the screen.
If you have any questions, please consult Apple’s support website.
