Delete books from your Mac
When you delete a book or PDF it’s no longer stored on your Mac.
Select the book, then press the Delete key.
If you’re using iCloud for iBooks and you delete a PDF or book that you imported, it’s deleted from all of your devices.
Books you purchased from the iBooks Store are still in iCloud, even if you remove them from your Mac. They appear in your library with an iCloud status icon . You can download purchased books again from the iBooks Store, or simply double-click a book in your library that has an iCloud status icon. (You must be connected to the Internet.)
You can’t delete books you purchased in the iBooks Store from iCloud, but you can hide them (click Sort By, then select Hide iCloud Books). To hide books so they’re never in your library on any device, see Hide purchased books.
If you’re using iCloud for iBooks, PDFs and books you add on another device are automatically downloaded to your Mac as long as you have enough storage space. To turn off automatic downloads, you need to turn off iCloud for iBooks. Choose Apple menu > System Preferences, then click iCloud. Click Options next to iCloud Drive (make sure iCloud Drive is turned on), then deselect iBooks.