Deleting a book fails with `SqliteError: FOREIGN KEY constraint failed` and the book stays in the UI

I uploaded a bad EPUB, then uploaded a corrected copy, and now I can't get rid of the duplicate. Deleting from the UI just bounces me back to the main page with the book still listed, and the server log shows ERROR: FOREIGN KEY constraint failed / SqliteError. I even deleted the file from the filesystem and it still won't leave the UI. Running 2.14.10.

Resolution: The delete relies on cascade deletes, but some related entities aren't cascaded, so SQLite rejects the delete with a foreign key violation — and SQLite doesn't report which relation is at fault, so you have to find it by elimination. The reliable workaround: open the book's edit/settings page and remove its relations one at a time — author/creator, narrator, series, collections, tags — then delete the book. In practice the author relation is the usual offender; clearing it makes the delete succeed immediately. Deleting the underlying files from disk does not help and actually makes things worse, since the row stays in the database with no file behind it. This was fixed shortly after 2.14.10, so upgrading is the permanent answer; the same root cause produces the "deferred/removed book keeps reappearing in the book list" symptom.