Amazon's newest perk for Prime members goes back to its bookworm roots.

On Wednesday, the company came out with Prime Reading, which provides a rotating library of over a thousand books, with current titles including "The Hobbit," "Harry Potter and the Sorcerer's Stone" and "The Millionaire Next Door." The free service, available only to Prime members in the US, also includes changing selections of comics, kids' books and magazines, including National Geographic Traveler, People and Sports Illustrated.

The service is available on iOS and Android devices using the free Kindle app, as well as on any Amazon Kindle e-reader or Fire tablet.

Prime Reading adds to Amazon's continually expanding list of Prime services, which the company uses to entice customers to keep forking over its $99 annual membership fee. Maintaining those millions of Prime members is important for the online retailer, since those buyers tend to spend roughly twice as much on its site as non-Prime shoppers.

While a useful addition, the new perk likely won't bring in droves of new members the same way as other popular services, such as Prime's unlimited, two-day shipping or the Prime Day shopping holiday.

However, all the additional reading sparked by Prime Reading could help drive more sales of e-books, a market Amazon helped birth and still dominates. Also, Prime Reading may serve as a gateway to get more of Amazon's loyalest customers to sign up for Kindle Unlimited, Amazon's $10 monthly reading service that includes over 1 million books and thousands of audiobooks. Using a similar tactic, Amazon last month introduced a slimmed-down, free-for-Prime version of its paid audiobook services called Audible Channels. A full Audible membership costs $14.95 a month.

In addition to Prime Reading, Amazon will continue to provide the Kindle Owners' Lending Library. That Prime service lets people borrow one e-book a month from a much wider selection of hundreds of thousands of titles. Unlike Prime Reading -- which can be used with Amazon, iOS and Android devices -- the lending library is only available on Kindle and Fire devices.

Adding to the list of new Prime services, Amazon last week created Twitch Prime, which strips out ads for Prime members on its Twitch video-streaming service for live video-game sessions, talk shows and other broadcasts.