If you want to just blow the data damage off, then you really don’t want my money - ever. Trust my hard earned experience, there is one. Just because many users have no problems doesn’t mean there is no bug. Did you bother to ask if there was Time Machine back up did you reach out to help restore? Database corruption bugs is one the of the most important bugs and hardest to test for. And had to hand hold users whose data is gone - its painful. I have seen and reported app bugs that corrupt a database file making migration during updates break. Launch the program, then connect your iPad cable to the bottom of your iPad and to an available USB port.
This will allow you to drag and drop PDF, EPUB files from your iPad Pro to computer. This will automatically download all the iBooks you selected from your iTunes. Bluefire Reader Step One Select the Bluefire Reader icon on the iPad Step Two Select Authorize on the Authorize this app now message. Right-click on the iBook and select Download. I have been doing QA for many decades (am 57) for many companies with many different products. Find the iBook/s that you wish to download on your device. I think it is unavoidable that some upgrades may have a problem. There are many other users upgraded without any problem. Tap on Settings >Account Profile >iCloud > Books (iBooks) and turn the setting to back ON. Locate the Books/ iBooks icon here and switch it to the off position by tapping on the slider. I am about to buy but this bug makes me want to wait. Tap on iCloud and scroll down to the section with the heading ‘APPS USING ICLOUD.’. Something went wrong when migrated on the new datastore. Your case is the second among 3500 updates till now.
But saw some reports of users book library get wiped out during the v5 update.