Marx's earliest work is positioned squarely in the intellectual discussion of his day; works like On The Jewish Question are primarily of historical interest, as they deal with situations long since changed. His principal works are The German Ideology and The Communist Manifesto (both co-written with Engels), and his lengthy economic analysis Capital, one volume of which was published during his lifetime, the other two of which were edited by Engels and released posthumously.

Writings by Karl Marx

The Philosophical Manifesto of the Historical School of Law (1842)
Critique of Hegel's Philosophy of Right, 1843
On the Jewish Question, 1843
Notes on James Mill, 1844
Economic and Philosophical Manuscripts of 1844, 1844
The Holy Family, 1845
Theses on Feuerbach, 1845
The German Ideology, 1845
The Poverty of Philosophy, 1847
Wage-Labor and Capital, 1847
Manifesto of the Communist Party, 1848
The Eighteenth Brumaire of Louis Napoleon, 1852
Grundrisse, 1857
Preface to A Contribution to the Critique of Political Economy, 1859
Writings on the U.S. Civil War, 1861
Theories of Surplus Value, 3 volumes, 1862
Value, Price and Profit, 1865
Capital, Volume I (Das Kapital), 1867
The Civil War in France, 1871
Critique of the Gotha Program, 1875
Notes on Wagner, 1883
Capital, Volume II [posthumously published by Engels], 1885
Capital, Volume III [posthumously published by Engels], 1894