Goodreads, a social networking site for readers, has grown its membership to 10 million members. Collectively, these users have shelved 360 million books (chart embedded above).

The rate of growth has gained momentum in the last year and a half. The site earned its first 5 million members in four and a half years, and doubled its membership from 5 million members to 10 million members in the last 18 months.

Goodreads founder Otis Chandler blogged the news: “When we first launched in January of 2007 we waited until we hit what then seemed like a magical number of 100,000 members before we hired our first employee and secured angel funding. Since then, the vibrant Goodreads community and company has continued to blossom. We now have a team of 30, we’ve just moved into bigger, fancier offices in San Francisco, and we’ve launched an array of new products, including our super-awesome and successful Recommendations Engine.”

Goodreads has great resources for tracking popular titles and discovering reader preferences. For example, Goodreads discovered that dystopian fiction is more popular now than it has been in 50 years and made this infographic about the findings. The site recently launched a tool to make it easy to add Goodreads updates to your Facebook timeline. Follow this link to find out how.