Amazon is returning back to their bookseller roots.

This past Tuesday, the online retailer introduced a new service, Prime Book Box, a subscription service that offers organized boxes of hardcover books for kids up to age 12. Customers can choose whether to receive the boxes either every one, two, or three months. The service cost $23 a box, which according to Amazon, customers will save 35% off the list price.

As of right now, the subscription service is only available by invitation only to Prime members. Four board books will be available for the baby to age 2 group. Two hardcover books will be available for the other three age groups: 3 to 5, 6 to 8, and 9 to 12. This can be a beneficial service, especially for parents and children who live in areas where they don’t have access to either a bookstore or a library.

To learn more about the new subscription service, visit Amazon’s website.