Books deleting library after startup

Question

Yesterday Books began deleting all books in my library except for a proof generated by Books author, and four books purchased from the Apple store. I replaced the directories ~/Library/Containers/com.apple.iBooksX and com.apple.BKAgentService from backup to restore the library. Books deleted them again.

I upgraded to 10.14 from 10.12, and disabled syncing, the behavior persists.

Answer 1

I had to give up and download my entire library from iCloud.