Contrary to what many mainstream macroeconomists seem to think, modern, globally interdependent economies, financially as well as otherwise, can be hit hard by economic downturns. That is the lesson learnt from the years of the Great Recession and the Covid-19 pandemic. Macroeconomics is not just about supply-side aspects. Such a focus is much too narrow. Important demand-side matters must be accounted for as well. As such, there is an imminent need to present an alternative to the modern macroeconomic mainstream understanding. Alternatives do exist. In the present book we argue that post-Keynesian advocacy is urgently in demand.