Amazon has launched yet another Prime perk for members across the U.S.

The latest benefit isn’t a free offering, like many of the other perks that come as part of an annual Prime membership. For $22.99, you can beckon a box containing a selection of children’s books — and you can set this delivery to recur on a monthly, bi-monthly, or quarterly basis.

The ecommerce giant debuted the Prime Book Box service for kids aged 0-12 back in May, though it was just available on an invite-only basis until today. Now, it’s ready for Prime time.

Above: Prime Book Box

Though Amazon has built a veritable ebook empire via its array of Kindle ereaders, children are more likely to engage with colorful, engaging, and interactive physical books, which is the underlying tenet of the Prime Book Box. Indeed, each box will contain either two hardcover books or four sturdy “board” books.

Though the Prime Book Box is an extra expense on top of a Prime subscription, it still serves to encourage more people to sign up for the Prime service. For one thing, it saves parents from having to wade through list upon list of recommended children’s books, as Amazon does all the spade work on their behalf. But over and above all that, Amazon promises that you can save as much as 35 percent on each book’s list price.