Revisiting Classical Economics

The financial crisis and the economic crisis that followed triggered a crisis in the subject of economics, as it is typically being taught today especially in macroeconomics and related fields. A renewed interest in earlier authors, especially the classical economists from Adam Smith to David Ricardo and John Maynard Keynes, developed. This book may also be seen as a response to this interest. What can we learn from the authors mentioned, what we could not learn from the mainstream?