This article assess two important recent books on Marx's political economy and argues that, despite many virtues, there are some crucial limitations in their approach to Marx's political economy. Ben Fine's and Alfredo Saad-Filho's Marx's 'Capital' and The Value of Marx by Saad-Filho place too much explanatory weight on the composition of capital, giving too little attention to Marx's analysis of money, and to the processes of circulation and realisation.