Amazon has quietly launched something called Prime Book Box.

Essentially, it's a monthly book subscription service for kids. If you subscribe, you will receive (delivered to your door) a box with four board books or two hardcover picture books or novels. This is Amazon's first monthly subscription service in which it offers physical books. Here's everything you need to know about it and how it works.

Prime Book Box is a paid subscription service where you receive a box of children’s books every month, two months, or three months. Each box contains four board books (for ages two and younger) or two hardcover picture books or novels (for ages three to 12). Amazon said you'll save up to 35 per cent off the list price of these books.

When the service officially launches, you'll need to subscribe and then choose how often you'd like a box.

Depending on the plan you choose, the available books will be divided into four different age groups for readers: birth to two years, three to five years, six to eight years, and nine to 12 years. Amazon's editors will pick the books for your selected age range. And they will use your purchase history to avoid books you've already bought.

Amazon said its editors "read thousands of books every year to find selections your reader will enjoy again and again," and that "you'll discover new releases, classics, and hidden gems tailored to your reader's age".

If you're worried about the books being hand-picked, don't fret. Each month, you will receive an email preview of the box, and you can choose to swap some books from a short list of alternate options before the box is shipped.

Amazon said every box will ship free to your door. And you can skip a box at anytime.

Below are a few examples of the books you could receive:

1/4Amazon

It costs $22.99 a month.

Like most other new services from Amazon, Prime Book Box is currently only available by invitation, and it's exclusive to Amazon Prime members in the US. You can request an invite here.

  • To learn more about how Amazon Prime works, go here.

Check out Amazon's Prime Book Box page for more details.