Karl Marx's main ideas are labor theory of value, class struggle, alienation and communism. He is the co-founder of Marxism and has published many books, the two most famous being "Das Kapital" and "The Communist Manifesto."
The "Communist Manifesto" was published in 1848 and was written for the Communist League. It is currently one of the world's most influential political documents. It details the problems with capitalism and how it would eventually be replaced by communism. It also identifies Marx's ideas on society progression and class struggle. Published in 1867, "Das Kapital" describes how the exploitation of labor drives capitalism within society.