Steven Levitt is clearly a brilliant man. An intellectual that isn't afraid to rock the boat with some controversial yet well-thought ideas. The book identifies some very interesting trends and presents them in a straight-forward readable manner.
However, Levitt's ideas are not explored in enough detail to sufficiently enforce his arguments. It almost seems that the publishers have dumbed it down to the level of the ordinary person in order to sell more books. I haven't read the expanded edition, but I hope Levitt provides some of the background that is lacking in this edition.