It was an unlikely book to take America by storm: a 700-page work of economic history by a French academic. But Thomas Piketty’s “Capital in the 21st Century” has proved to be a book for our times, explaining the extreme inequality that characterizes our world, and drawing some bold and empirically backed arguments about the inherent tendencies of the capitalist system. Piketty, in a rare US radio interview, discusses the roots of wealth inequality in the global North and South, war and revolution, and the current economic crisis. (Encore presentation.)