Keep your kids from buying books, or restrict them 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.
Keep kids from buying or downloading books with explicit content
Choose iBooks > Preferences, then click Parental.
Click the lock icon to change the parental control settings, then enter the administrator name and password for your computer.
Select options to disable all purchases and free downloads or restrict downloading books with explicit content.
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.
For more information about setting parental controls on a Mac, see Set up parental controls.