Animal Farm and 1984 by George Orwell. They both describe, in a very creative way, the totalitarian regimes of the '40s, especially the soviet one.
They give you an insight of what freedom should be, and what are the systems used by dictators to control the popultation: poverty, ignorance, fear, etc.
I've read both but Animal Farm was for school so naturally I didn't like it. 1984 was great not just as an interesting read but to understand all of the cultural (and culture war) references to it.