As any good soccer junkie, I devour any and all interesting-looking books on soccer. I just finished Jim Haner's Soccerhead: An Accidental Journey into the Heart of the American Game (2006, North Point Press). If you are at all curious about the game in the US, or about youth sports in general, I recommend this book. It offers humorous accounts of a no-nothing youth soccer coach (Haner), and his metamorphosis into a full-fledged soccer nut.
It also offers insight to the history of the game in the US. Haner describes how the game predates American football, basketball and baseball by a significant margin, and offers some explanation of how it lost it's status as an American sport over time.
In addition, Soccerhead offers reminders about the nature of youth sport, and the role of parents in youth athletics. Haner interviewed many experts, and spoke from his own experience. The second-most important point, specifically related to soccer, is that the best coaches at the youth level coach the least. The most important point, and this is relevant to all youth sport, is that it should be fun. Period.