For eighteen years, Bruce Bueno de Mesquita and Alastair Smith have been part of a team revolutionizing the study of politics by turning conventional wisdom on its head. They start from a single assertion: Leaders do whatever keeps them in power. They don’t care about the “national interest”—or even their subjects—unless they have to. This clever and accessible book shows that the difference between tyrants and democrats is just a convenient fiction. Governments do not differ in kind but only in the number of essential supporters, or backs that need scratching. The size of this group determines almost everything about politics: what leaders can get away with, and the quality of life or misery under them. The picture the authors paint is not pretty. But it just may be the truth, which is a good starting point for anyone seeking to improve human governance.