The author is a theoretical physicist. But there are no equations in the book. Someone with a middle school math education could, theoretically, understand the message. Still, some of the arguments are subtle.
This book considers the particular subfield of Complexity Theory called Social Physics or Agent-based Social Simulation.
Computer simulation of people, corporations, and economies has generated results that qualitatively resemble real-world phenomena. Specifically, the same power laws appear.
There are more small corporations than large corporations. Economists have noticed that the number of corporations of wealth W varies inversely as S squared. For example, there are 9 times as many corporations with sales of 1 million dollars as there are corporation with sales of 3 million dollars; 3*3 = 9.
Similarly, there are more small rivers than large rivers, and scientists have determined that the number of rivers with amount of water W flowing through them varies in inverse proportion to W to the power 1.43 or so. Similarly, there are more poor people than rich people, and the number of people with wealth W varies inversely to about W to the power 2.5. (For example, there are about six times as many people have a million dollars as there are people having 10 million dollars.) And the number of stock price changes of size S varies inversely as S squared, the number of avalanches involving N grains of sand varies inversely as S raised to some power, etc, etc.
Well, it turns out that computer simulations of simplifed people, corporations, grain sands, and so on have replicated many of these power law phenomena. Moreover, the simulations give insight to what's going on.
Complexity theory's predictions aren't as precise as the predictions of, say, Newtonian physics, but in fact much of modern physicis is statistical in nature.
Computer simulations can help explain why racial segregation occurs, even in the absesnce of bigotry. For example, suppose people of various races are thrown together in a city, living amongst each other in an integrated way. If racism is rampant (for example, it people prefer all or most of their neighbors to be of the same race), then it is likely, of course, that over time people will relocate and segregate into enclaves of same-race people. It turns out that even if people are not racist segregation will occur. Specifically, suppose people are OK with living amongts people of other races, as long as no more than 70% of their neighbors are of a different race. (According to the this argument, such people aren't really racist. They're OK with having even 60% of their neighbors be of another race. They're just uneasy if they're in the distinct minority.) Well, computer simulations suggest that even in these conditions, segregation will naturally occur. What happens is that by chance some small neighborhoods will have a predonderance of one race and a dearth of another race. People of the minor race will naturally move away because they're the extreme minority. Over time, such enclaves will grow, and segregation will naturally arise.
Skeptics may wonder whether the power law analogies are strong enough to warrant all the fuss about Complexity Theory. I, and many others, find the research area valuable because of the insights it gives into phenomena such as human cooperation.
Despite Bucahan's advanced scientific training, the book's message is largely ethical. The author explains the evolutionary origins of cooperation and the implications for economics and politics.
According to classical and neo-classical economic theories economics, humans are rational, selfish creatures who try to maximize their gains and minimize their losses. This view of humans is incomplete. Humans aren't always rational (for example, they're bad at many statistical estimates), and they often sacrifice their own well-being for the sake of others -- not just family and friends, but sometimes even strangers. Why do humans sacrifice their own well-being for others? Isn't it irrational to do so? (Economic conservatives apparently think so!) From a biological point of view, cooperation with family and kin makes some sense, since they share genes with you. Aside from the biological reasons, there are practical reasons. It makes sense to cooperate with people you're likely to meet again, even on self-interested, selfish grounds, since the others are likely to reciprocate later on. You scratch my back and I'll scratch yours.