With this slim book, you can come a long way in understanding the logical and practical essence of Marx's thought, which for me is contained in the idea of 'Praxis,' that there is no nature and no human nature per se, but both are dialectically interdependent, and thus humans shape their social circumstances as much as they are shaped by them. Human beings transform nature and through doing so transform their own nature -- and that is the essence of human nature, that it is plastic.
Avineri takes you step by step through the most fundamental concepts that Marx developed all his life (refuting, along the way, the idea that there is a 'break' between the early and the mature Marx), including alienation, labor, property, capital, praxis, revolution, the state, the abolition (Aufhebung) of the state and of property, and he does this through close and thorough readings of everything Marx ever wrote, including little unpublished notes and letters.
There is more here than can be digested after one reading, so I'm working through it more slowly now. The first couple chapters on Hegel and the idea of the universal class are difficult. The book then opens up in chapters 3-5 and these are the most crucial for me: this is where we get Avineri's treatment of the idea of praxis. Implicit in these chapters is a powerful critique of the foundations of contemporary economics as well as ecology. The last few chapters are solid but not as mind-blowing as the previous, which seem to lay out the living heart of Marx's thought and show how Marx took Hegel's achievements and developed a philosophy whose purpose was to transform the world. And Avineri makes a convincing case, as did Marx, that philosophy can be logically shown to transcend itself and become a revolutionary force. Indeed, this is philosophy's destiny, spurred on by its own inner logic. Damn.
This is one of the best things I've read on dialectics, which Avineri explores through how Hegel and Marx used the term 'Aufhebung,' which is a paradoxical word meaning at one and the same time abolition, transcendence, and preservation. You could study this concept your whole life, it seems, and, naturally, never get to the bottom of it.
Avineri never once allows his own voice to come through in the text, so loyal he is to expounding his subject -- until the epilogue. Then Avineri puts his enormous labor to use and in the span of a few pages develops an immanent critique of Marx that will leave you stunned. Avineri is a master, and shows how Marx enthusiasts can live up to Ashis Nandy's standards by locating an ideology's wrong turns not as impure divergences from the ideology but as internal to the logic itself. Avineri shows, in stark logical form, why Marx's theories were interpreted to create a Stalinist regime. Yet you are left feeling that this is not a shortcoming of Marx's theory -- on the contrary, it is a startling testament to theory's power to affect the real world. It gives the lie, and this whole book gives the lie, to those that would insert a firm boundary between theory and action.