Are there any good critical discussions, if not refutations, of communism, especially its philosophical concepts, e.g. theory of knowledge, communist materialism, dialectics etc.?
Probably Karl Popper's work comes the closest. Get his book (I believe in two volumes) on the enemies of a free society. His work was taken seriously by eastern Europeans who were under the authority of the Soviet Union. Popper provided them with an alternative perspective by which to offer a critique of communism. Popper's work is systematic and fair (except in the case of his critique of Plato, which I believe to be based on a partial misreading of Plato) and historical. A book that is less historical but is profoundly anti-collectivism (and thus communism) is Robert Nozick's Anarchy, State, and Utopia. The latter is full of great arguments, colorful examples, and well worth a slow read.