Politics, both of contemporary affairs and the ideological kind. And history. And Socialist revolution.
Working men of all countries, as humanity and working class exploitation transcend the boundaries of nationality, race, and religion, and you have nothing to lose but your chains.
The unfortunate nature of capitalism has turned all forms of art into profit making industries, and now all artists have become wage labourers of the cpitalist system. Once a socilist society has been established, music will no longer be about what makes money and what the record companies can sell, but about creativity and imagination. After socialism has been established all forms of music will therefore be superior in thier artistic nature than any current forms of mass produced, made to sell, music.
The same as music, only applied to film
Obviously the communist manifesto is the one you should all be reading, however, iv a certain liking for Freud's "the interpretation of dreams." Thomas Hobbes "leviathan" and Adolf Hitler's "Mein Kampf," although inherently wrong on their interpretations of human nature, among other things, are still important to read and understand, so that they can be properly criticised.
Freidrich Engels, Georg Hegel