| 1905 | Industrial Unionism✓Free — An Address | Eugene Victor Debs | English |
| 1905 | Principles of Industrial Unionism✓ — An Address on the Preamble of the Industrial Workers of the World | Daniel De Leon | English |
| 1906 | Socialism✓Free — A Paper Read Before the Albany Press Club "Socialist Night" | William Scholl McClure | English |
| 1907 | The Capitalist ClassFree | Karl Johann Kautsky & Daniel De Leon | English |
| 1907 | The Class Struggle✓ | Karl Kautsky | English |
| 1907 | The Development of Socialism in Great Britain✓ | Socialist Labour Party of Great Britain. National Executive Committee | English |
| 1907 | What Means This Strike?✓Free — Address | Daniel De Leon | English |
| 1908 | The Burning Question of Trades Unionism✓ | Daniel De Leon | English |
| 1908 | The Preamble of the Industrial Workers of the WorldFree — Address Delivered at Union Temple, Minneapolis, Minnesota, July Tenth, 1905 | Daniel De Leon | English |
| 1908 | Two Pages from Roman History✓Free | Daniel De Leon | English |
| 1911 | Shop Talks on Economics✓ | Mary E. Marcy | English |
| 1912 | Industrial Workers of Great Britain✓ — Industrial Unionism | — | English |
| 1912 | Taxation by John D. Goerke [and] Who Pays the Taxes? A Dialogue by Daniel De Leon✓ | — | English |
| 1914 | Boehm-Bawerk's Criticism of Marx✓ | Rudolf Hilferding | English |
| 1914 | The Collapse of the Second InternationalFree | Vladimir Il’ich Lenin | English |
| 1916 | Socialism Made Easy✓Free | James Connolly | English |
| 1917 | International Socialism and the Proletarian Revolution in Russia✓ | Grigorii Evseevich Zinov'ev | English |
| 1917 | Militarism and Anti-militarism✓Free — With Special Regard to the International Young Socialist Movement | Karl Liebknecht | English |
| 1917 | The State✓ — Its Origin and Function | William Paul | English |
| 1918 | Capitalism in the South Wales Coalfield✓ | Geo Harvey | English |
| 1918 | Equality of Sacrifice✓ — A Criticism of the Capitalistic Treatment of the Victims of the War, and an Alternative | J. T. Murphy | English |
| 1918 | Hands off Russia✓ — An Analysis of the Economics of Allied Intervention in Russia Harvard College Library Preservation Digitization Program | William Paul | English |
| 1918 | Revolution and Counter-revolution or Germany in 1848Free | Karl Marx & Eleanor Marx Aveling | English |
| 1918 | Scientific Socialism✓Free — Its Revolutionary Aims and Methods | William Paul | English |
| 1918 | Scientific Socialism, Its Revolutionary Aims & Methods✓Free | William Paul | English |
| 1918 | Scientific Socialism, Its Revolutionary Aims & Methods, by Wm. Paul✓Free | Paul, William, b. 1884 | English |
| 1918 | Socialism✓Free — Utopian and Scientific | Friedrich Engels | English |
| 1918 | The Socialist Programme✓Free | Karl Marx | English |
| 1918 | The State: Its Origin and Function✓Free | William Paul | English |
| 1918 | War or Revolution?✓ — Bolshevist Socialism Versus Capitalistic Imperialism | Lev Davidovič Trockij | English |
| 1919 | Boehm-Bawerk's Criticism of Marx✓ Nineteenth Century Collections Online: British Politics and Society | Rudolf Hilferding | English |
| 1919 | Capitalism in the South Wales Coalfield✓ | George Harvey | English |
| 1919 | Increased Production from a Worker's Point of View✓ | George Daggar | English |
| 1919 | Karl Liebknecht✓ — The Man, His Work, and Message | William Paul | English |
| 1919 | Labour and Empire✓ — A Study in Imperialism | William Paul | English |
| 1919 | Militarism and Anti-militarism✓Free — With Special Regard to the International Young Socialist Movement | Karl Liebknecht & Alexander Sirnis | English |
| 1919 | Satires, Lyrics and Poems (Chiefly Humorous)✓ | John S. Clarke | English |
| 1919 | Six Weeks in Russia in 1919 | Arthur Ransome | English |
| 1919 | The Building of the New Russia✓ | — | English |
| 1919 | The Development of Socialism from Science to Practice✓ | Karl Radek | English |
| 1919 | The Great Initiative✓Free — Including the Story of "Communist Saturdays" | Vladimir Il’ich Lenin | English |
| 1919 | The History of the Russian Revolution to Brest-LitovskFree | Leon Trotsky | English |
| 1919 | The New Communist Manifesto of the Third International✓ | Communist International. Congress | English |
| 1919 | The State and Revolution✓Free — Marxist Teaching on the State and the Task of the Proletariat in the Revolution | Vladimir Il’ich Lenin | English |
| 1920 | First Principles of Working-Class Education✓Free | James Clunie | English |
| 1920 | Hands off Russia✓ — An Analysis of the Economics of Allied Intervention in Russia Social Science Series | William Paul | English |
| 1920 | Lenin's Thesis on Bourgeoise Democracy and Proletarian Dictatorship✓ | Vladimir Il’ich Lenin | English |
| 1920 | Programme of the World Revolution✓Free | Nikolaĭ Ivanovich Bukharin | English |
| 1920 | Through Dictatorship to Democracy✓Free | Klara Zetkin, Eden Paul, Cedar Paul & Spartacus Group | English |
| 1921 | Red Europe✓Free | Frank Ansty | English |
| 1921 | The ABC of Communism✓Free — A Popular Explanation of the Programme of the Communist Party of Russia (the Bolsheviki) | Nikolaĭ Ivanovich Bukharin | English |
| 1921 | The Third (Communist) InternationalFree — Its Aims and Methods | James Clunie | English |
| 1942 | Socialism and the State✓ | Socialist Labour Party | English |
| 1950 | Marxism Versus Stalinism✓ | Socialist Labour Party | English |
| 1980 | Boehm-Bawerk's Criticism of Marx✓ | Rudolf Hilferding | English |
| n.d. | Development of Socialism from Utopia to Science | Engels, Frederick. Trans. By Daniel de León | English |
| n.d. | Reform or RevolutionFree | Daniel De Leon | English |
| n.d. | Revolutions and the Intelligentsia | Jack Nichol | English |
| n.d. | The Socialist Reconstruction of SocietyFree | Daniel De Leon | English |
| n.d. | The Working Class | Karl Kautsky | English |
| n.d. | Value, Price and ProfitFree | Karl Marx | English |
| n.d. | Wage-Labour and CapitalFree | Karl Marx | English |