system
Given the following post, respond as if you're commenting on Reddit:
human
What’s the best book about the history and theories of Marxism since Marx and Engels?

I’m looking for a book that’s like the Marxist version of what Mitchell and Black’s “Freud and Beyond” were to psychoanalysis. The more theorists it covers, the better.
gpt
Leszek Kołakowski’s *Main Currents of Marxism* covers the various historical and theoretical developments of Marxism up to the year it was published (1976). Kołakowski is generally critical of Marxism throughout the work, but it’s still fairly balanced and is about as thorough a treatment you’re going to get in a single book.