Delete books or audiobooks from your Mac in Books
When you delete a book, audiobook, or PDF from your library, it’s no longer stored on your Mac.
In the Books app
on your Mac, click All Books in the sidebar.Select the book or audiobook you want to delete, then press the Delete key.
If you’re using iCloud for Books and you delete a book or PDF that you imported, it’s deleted from iCloud and all of your devices where you use iCloud for Books.
Items you purchased from the Book Store or Audiobook Store are still in iCloud, even if you remove them from your Mac. Purchased books appear in your library with an iCloud status icon 
. You can download purchased books and audiobooks again.
You can’t delete items you purchased from the Book Store or Audiobook Store from iCloud, but you can hide them; choose View > Hide iCloud Books. To hide books and audiobooks so they never appear in your library on any device, see Hide and unhide purchased books and audiobooks.