Dive Brief:

• Amazon on Tuesday said that it expanded its Prime Book Box, a subscription delivering curated children’s books every one, two or three months. The subscription is now available to all of its U.S. Prime members, according to a company press release. 

• Each box is $22.99, which Amazon said reflects discounts of up to 35% off list prices, and can be geared to children ages 0-2, who get four board books, or ages 3-5, 6-8 or 9-12, who get two hardcover books.

• Amazon editors curate the boxes, but subscribers can adjust the contents before they’re sent out. Amazon started testing the subscription in May by invitation only. 

Dive Insight:

As it first tested this subscription, Amazon's portrayed the children's book box as a fun, Christmas Day-like experience for kids that fosters reading and snuggling on the couch with mom and dad. It could be well positioned to withstand the mercurial nature of subscription customers, 40% of whom ultimately cancel, according to recent research from McKinsey and Co.

But as one of the few new perks for Prime members, it's pretty limited. Prime members enjoy a host of benefits, including an entertainment streaming service rivaling Netflix, limited music streaming, photo storage, exclusive access to certain Amazon private labels and, the one most people use it for, free two-day shipping on millions of items through Amazon itself as well as its marketplace — along with a host of exclusive discounts.

Other benefits, like Prime Now's one-hour same-day delivery, unlimited music streaming, Amazon Fresh grocery delivery, Kindle e-book subscriptions and now this kids book subscription, all cost extra.

This one may be a curious move, considering that, as TechCrunch notes, several startups — including Sproutkin, The Little Book Club and Zoobean — couldn't make a go of children's book subscriptions. Of course, Amazon has a formidable retail operation with a wide assortment and a highly lucrative cloud services unit to support it.

One advantage of a children's subscription service is that the customers are always growing, making replenishment and replacement necessary. Gap and Target have launched subscriptions with similarly flexible delivery and curation to capture that market in apparel.

But it could be hard to compete with actual bookstores, which offer enticements like story hour and playtime to entice little customers and their paying caregivers into stores. Independent booksellers, stung two decades ago by Amazon's arrival, nevertheless continue to thrive, and much of their success comes from their ability, as physical retailers, to offer events, readings and spaces designed for browsing.

One bookseller that continues to struggle despite that advantage is Barnes & Noble, which has finally gained a little traction more recently but experienced yet more turnover in the chief executive office just weeks ago.