Volume 41 contains Marx and Engels letters from January 1860 to September 1864 when Marx, continuing the elaboration of his economic theory, wrote the second rough draft of Capital (the manuscript of 1861-63), whose complex genesis the letters make it possible to trace stage by stage. The volume reflects Marx and Engels interest in political affairs and gives an idea of their work as correspondents of the New York Daily Tribune and Die Presse. The correspondence shows Marx and Engels as the leaders of the German working-class movement. Of fundamental importance is their assessment of the role played in the movement by Ferdinand Lassalle and their critique of his reformist and sectarian programme and tactics. In addition, the letters are a valuable source of biographical data on Marx and Engels. Of considerable interest in this respect are the letters of Marx’s wife Jenny and their daughter Laura, given in the Appendices.