This is a new revised edition of a book which has come to be widely recognized as the best and simplest introduction available to Marxist economic theory. In a very lucid style, carefully defining all the technical terms used, it provides a comprehensive treatment of "the law of motion of capitalist society" which Marx expounded in the three volumes of Capital: origins of capitalism; surplus value; rent, interest and profit; capitalist accumulation; circulation of Capital and economic crisis; imperialism; distribution of the national product.