The Polish economist Michal Kalecki (1899-1970) was one of the architects of the Keynesian Revolution in economic theory and policy who came to England soon after the publication of Keynes's General Theory. Jan Toporowski's intellectual biography of Kalecki brings to the general reader, as well as professional economists, an explanation of the key ideas of Kalecki and how these differed from the theories of John Maynard Keynes. The book contains a wealth of new material on Kalecki and Keynes's circle in Cambridge, their shared ideas and disagreements. Kalecki's discussions of the business cycle, the New Deal, and the respective economic policies of the Popular Front in France, Nazi Germany and inter-War Poland, changed the Economics of the twentieth century. Jan Toporowski's lively and accessible discussion of Kalecki's intellectual development casts important new light on Economics and economic policy in a time of instability and financial crisis.