permanently delete (library) books

Hello,

I've been trying to get rid of dead ebooks on my pc and

searched every folder I could think of for rouge copies of

the books for which the licences have ended.

Adittionally I tested forbidding and allowing cloudsync.

But this dead books just keep showing up in ade no matter

how often I delete them.

How can I fix this?

I am looking forward to suggestions