This book provides an accessible introduction to Marx's seminal work Capital and explores the core ideas of Marxian political economy relevant for modern day economies. The first part gives an overview of Capital based on the authors' original thinking in the methodology of Capital. The second part discusses the application of these ideas to some understudied questions of measuring profit on alienation, the rate of exploitation, the reconstruction of input-output tables, and the role of the welfare state and social wage. The third part sets forth new research in Marxian analysis in the 21st century, facing the challenges brought about by digital labor and the deep crisis of the global economy. The last part discusses the Marxism/Neo-Ricardianism controversy.