We live in a world in which human capacity to transform and control our lives has never been greater. Yet for most people the world is radically outside of their control. Their lives are dictated by the demands of employers and politicians. This is the phenomenon of alienation that the young radical Karl Marx began to diagnose in the early 1840s and remained pre-occupied with throughout his life.This accessible guide to the central aspect of Marx's philosophy takes the reader through the development of the concept and its relevence today.