The books and audiobooks you purchase in the Books app are saved in your library and automatically sorted into collections, such as Audiobooks, Want to Read, and Finished.
Navigate to a book, then tap on your iPad.
Navigate to a book or audiobook you want to remove, then tap on your iPad.
Tap Library, then tap Collections.
Swipe left on the collection you want to delete, then tap Delete.
Note: Deleting a collection doesn’t delete the books or audiobooks in the collection; they’re still in your library.