Import books or PDFs in Books on Mac
If you have books that you didn’t get from the Book Store or PDFs that you want to open in Books, you can import them into Books.
In the Books app on your Mac, choose File > Add to Library.
In the Open dialog, select the books or PDFs you want to import, then click Add.
If you have books in iTunes that you want to add to your Books library, you can choose File > Move Books from iTunes.
If you have imported books and PDFs on your other devices, you can use iCloud for Books to see them on your Mac.