Per Wikipedia:
Quote
Marx's theories about society, economics and politics—the collective understanding of which is known as Marxism—hold that human societies progress through class struggle: a conflict between an ownership class that controls production and a dispossessed labouring class that provides the labour for production. States, Marx believed, were run on behalf of the ruling class and in their interest while representing it as the common interest of all; and he predicted that, like previous socioeconomic systems, capitalism produced internal tensions which would lead to its self-destruction and replacement by a new system: socialism. He argued that class antagonisms under capitalism between the bourgeoisie and proletariat would eventuate in the working class' conquest of political power and eventually establish a classless society, communism, a society governed by a free association of producers. Marx actively fought for its implementation, arguing that the working class should carry out organised revolutionary action to topple capitalism and bring about socio-economic change.
Regardless of your opinion on Marx, he was very most likely a genius and has had a huge impact on modern day governments.
Personally, I find Marx and his ideas to be fascinating. The United States is closer to an oligarchy than anything else nowadays, so I think you can draw many comparisons to what he predicted with what is seen in the US.