This book is devoted to the lasting impact of The General Theory (and Keynes’s thought) on macroeconomic theory, methodology and its relevance for understanding the post-crisis challenges of the 21st Century. A number of contributions take their departure from Keynes's presentation during the 1930's of his new macroeconomic understanding and its policy implications. Other chapters take a more pluralistic view of Keynes's ideas and their importance for contemporary debates. Further, it is demonstrated that many textbooks often misrepresent The General Theory and therefore cannot be a reliable guide to 21st Century economic policy.