If you're not a fan of the current shift towards e-books and videos over traditional, paper books, Amazon has you covered. Their Prime Book Box, which was initially launched in May, would ship out a selection of books to kids on an invite-only basis for $23 per box.

These boxes could be customized by age, so a child between the ages of nine and 12 would receive a different set of books than a four-year-old. This bundle contained 2 hardcover books or four "board" books; either way, Amazon said the Book Box could save customers "up to 35%" off of the list price of each book.

This was certainly an intriguing idea, but the invite-only restriction was a bit disappointing. Fortunately, in a press release published today, Amazon announced that their Book Box program is rolling out on a subscription basis to all US-based Prime users.

For the same $23-per-box price, subscribers will be able to select their child's book genre preferences and let Amazon do the rest. As was the case with the invite-only test program, the Book Box will contain two hardback books or four board books depending on a given child's age.

If you want to try the service out with your own children, you can choose to receive a shipment every 1, 2, or 3 months. To get started, visit the official Book Box web page with an active Prime membership and create a Reader Profile for your kid.

This expanded version of Prime Book Box will undoubtedly please children and parents, but it would be nice to see Amazon expand the program to cover more age groups. As an avid paperback reader myself, I could get quite a lot of value out of a service like this.