Why is society organized the way it is? Is it possible to use some of the laws of the physical universe to understand why and how national economies, stock and commodity markets, companies and clubs organize the way they do? Can physics provides "laws" of human nature that are as useful and universal as those of mechanics? Does the critical point in a phase diagram have analogies in human behavior? Veteran science writer and physicist/chemist Philip Ball writes very well, as evidenced by Elegant Solutions, which was one of my picks last year. He also thinks very well, as evidenced by this creative application to sociology of concepts familiar to physicists and chemists. Of course, social scientists have always tried to be as "scientific" as possible, using mathematical models, statistical analysis and, more recently, computer simulations to understand the human situation and to predict its future. Critical Mass uses a different approach: using whole concepts in physics for insight into economics, urban planning, and the self-organization of human networks. This is a very original and thought-provoking book; it has already been recognized with the 2005 Aventis Prize for Science Books, bestowed annually by the Royal Society for Chemistry.