I've followed his blog on and off for a couple of years. I like statistics, data and demographics, and this book is nirvana for that. (Disclosure, I met my now wife on OkCupid, so I owe them an upvote here)

This is written by @christianrudder, one of the cofounders of OkCupid. Their blog, OkTrends, is one of the best examples of written content marketing. So many fascinating, data-driven observations.