Das capital is the book of Carl Marx in which the whole philosophy of Marxism or communism is.
which was for to give a new direction to the world in its political ,economical and social system, it was
against the economical ,political and social differences which rejects the class system,
it is a lengthy book.
but it will better that you search for the oxford short introduction of Marxism/communism.

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Life is what happens to you while you’re busy making other plans. –John Lennon