My most popular article based on page views is 4 Sites to Help You Decide What to Read Next. At the time I didn’t think much of the article but it got stumbled and each time someone reviews it on stumble the traffic spikes again. I guess a lot of people want to find books that are similar to ones that they really like.
Recently I came across BookArmy, which is a site for people who love books are reading. This site is more social than the ones in the earlier article in that the site connects you with other users who have similar interests.