For unfiltered information on the real state of the left and social movements in Germany, at the end of World War One, this is an excellent book. Of particular use, is his careful reconstruction of the tragedy of the March Action in 1921. After reading this, you will likely have a higher opinion of the German activists trained by Rosa Luxemburg (Paul Levi for one), and a lower opinion of the Russian "experts" who arrived from Moscow. Too much of the story from that era is filtered through ideological lens. Angress is a good antidote to this problem. Angress had a difficult life – a Jewish intellectual in Nazi Germany - and ended up living in the United States. Those difficulties did not prevent him from being a careful, accurate historian.