Rarely does a relatively unknown professor of economics publish a book that sells more than 200,000 copies in a few months. When critics accuse the same economist of being normative, political, of manipulating data, of misunderstanding basic economic theory, and of wanting to impoverish everyone, surely it must be because he is on to something. Other commentators, perhaps a bit prematurely, are claiming that his book is the economics book that will define twenty-first-century debate.