First Steps with Books
1 The Books app’s sidebar is divided into three sections; Apple Books shows what you’re reading now and offers two shop options; Library lets you view your book collection; In My Collections, you can organise them into categories.
2 If you’re already a Books user on your iPad or iPhone, you can access your books by clicking the All Books option under Library. Here you can see your book collection. Books not currently on your Mac have a cloud under the cover.
Click on a cloud, or the three-dots icon next to it, for options to download a book to your Mac, delete it