Amazon on Thursday announced its acquisition of popular book recommendation site Goodreads. Terms of the deal, expected to close in the second quarter, were not disclosed.

Founded in 2007, Goodreads now boasts more than 16 million members who participate in more than 30,000 book clubs on the site. In addition to sharing recommendations, it allows users to compare what they are reading, keep track of what they have read and would like to read, and post ratings and reviews.

For Amazon, Goodreads would provide something like a book-centered social network to help promote sales through its Kindle devices and Web site.

Currently, however, Barnes & Noble serves as Goodreads' preferred online retail partner. Book description pages typically feature a Barnes & Noble button, alongside another button for other online stores including Amazon, to click to make a purchase. It’s not hard to imagine that Barnes & Noble button changing to an Amazon button at some point.

An Amazon spokesperson responded only that “Goodreads is a place for all readers no matter what books they read or how they read them, and we expect to keep it that way.” The company says it would treat the book site like other acquisitions including IMDb and Zappos, allowing it to continue as a stand-alone entity while working with the company to develop new services.

According to paidContent, Goodreads sourced all of its book data from Amazon until last year, before deciding the company’s API was too restrictive and switching to book wholesaler Ingram. But company CEO Otis Chandler sounded an upbeat note: "We’re now going to be able to move faster in bringing the Goodreads experience to millions of readers around the world,” he stated.

Tom Mainelli, research director for tablets at IDC, said Amazon’s purchase of Goodreads was in line with the prior acquisitions like IMDb and Audible, aimed at building context around products. “They’ve amassed quite a collection,” he said. “It’s one thing, among others, they’re doing quite well versus Apple, for example -- adding some additional smarts to the content, making it stickier to keep people coming back.”

If Goodreads can be integrated more tightly with the Kindle and Kindle Books, it could help make the company’s signature device more attractive to readers. In addition to its Web site, Goodreads also has companion iOS and Android apps.

IDC projects that Android tablets, including the Kindle, will move past the iPad in market share this year, at 48.8%. The outlook is not as bright for dedicated Kindle e-readers. The research firm estimates that e-reader shipments overall fell to 18.2 million this year from 26.4 million in 2011. Shipments are projected to increase slightly this year and next before beginning a gradual and permanent decline in 2015.