When you sign up for Family Library, you'll be asked to enter a credit card to cover any purchases made by your family, but the account administrator/keeper of the family finances will be able to approve purchases for the other users or allow them to use their own credit cards or gift cards. Each family member can also set which purchased items will be shared to the communal library and which will stay only on their own device.

While all Google Play apps and media will sync across any of your family's Android devices, only books, TV shows and movies will be available to iOS users. (In other words, you can't sync that Android copy of "Monument Valley" to your sister's iPhone.) The service is live as of Wednesday morning, but will be rolling out to users over the next 48 hours if it doesn't immediately show up.

Finally, it's also worth nothing that Family Library is still separate from the Google Play Music family plan the company launched last December. Those subscriptions won't change, but that service is now available in 12 countries, including Ireland, Italy, New Zealand and Mexico.