Priestland is a great storyteller. I learned a lot from this book. It's a history of communist movements and communist rule, not a history of communist ideas as I originally expected. Since the scope of the book is extremely broad, some things are simplified, which is fine. The basic idea is that Marxism has three facets: Romantic, Radical, and Modernist (synthesized from Fourier, Babœuf and Saint Simon respectively) and the history of communism is depicted as a dance between these three. This model works very well I think.