Authorize your computer to get books
If you purchase books from the iBooks Store on other devices, you can see those books on your Mac by authorizing your computer. You can authorize up to five computers and iOS devices to use with your Apple ID account.
Authorize your computer
Choose Store > Authorize This Computer.
If you haven’t already, sign in using the same Apple ID you use on your other devices.
Deauthorize your computer
Be sure to deauthorize your Mac before you sell it, give it away, send it in for service, or make major hardware upgrades.
Choose Store > Deauthorize This Computer.
iBooks authorization is managed in iTunes. To learn how to see your authorized computers, deauthorize a computer no longer in your possession, and more, see the Apple Support article Deauthorize your computer using iTunes.