When compiling this list of the best relationship books of the past decade, some overriding themes were apparent: Men are sex-obsessed cave men. Women are under the mistaken impression that they're living inside a real-life romantic comedy. But true love and soul mates do exist. It's been a confusing decade for the sexes, but we're confident that we'll figure it all out eventually. Here, a list of the ten most iconic relationship books of the '00s.