Three books

The Iron Heel by Jack London, this is a classic novel about the class struggle.

The State and Revolution by Lenin, this is an explanation of how a socialist state should be organised and gives the lie to the argument that Stalinism was a continuation of Leninism.

The Transitional Program - this is the program of the Fourth International - anti-capitalist and anti-Stalinist, it is the foundation of many of the socialist ideas current today.