You can set preferences in iBooks that prevent people who use your Mac from accessing the iBooks Store and from getting books with explicit content. If you have Family Sharing set up, you can turn on Ask to Buy so that you’re asked to approve any purchases for certain family members.
Control access to the iBooks Store and explicit content
Choose iBooks > Preferences, then click Parental.
Click the lock icon , then enter the administrator name and password for your computer.
Disable the iBooks Store: Anyone using your Mac can view your library, but can’t open the iBooks Store.
Restrict books with explicit content: Anyone using your Mac can see the titles of explicit books in your library or the iBooks Store, but can’t access the books or see their descriptions.
When you’re done, click the lock again.
Turn on Ask to Buy
Ask to Buy is on by default for children under 13, and can be turned on for family members under 18. (Specific age limits may vary in different countries or regions.) For more information, see Set up Family Sharing.
Choose Apple menu > System Preferences, then click iCloud.
Click Manage Family.
Select the family member on the left, then turn on Ask to Buy on the right.
You can also control access to the iBooks Store and explicit content using Parental Controls preferences. For more information, see Parental Controls Stores preferences.