The title here is somewhat misleading, chosen presumably to attract attention. Which indeed it does and may well encourage people to pick the book up. But although there is some evidence that Hitler knew of Otto Weininger, there is nothing to suggest that he had actually read him or that he was in any way influenced by his writings – although the fact that Weininger seemed to be anti-Semitic would obviously have appealed. More interesting is the fact that James Joyce and Wittgenstein read and related to Weininger’s thinking – in fact James Joyce gets more of a mention in the book than Hitler. Be that as it may, Otto Weininger (1880-1903) was a controversial thinker and philosopher, a prominent figure in fin-de-siècle Vienna, and is now remembered for his extreme views on women and Jews. He is accused of being a self-hating Jew and his 1903 book Sex and Character became a cause celebre. His ideas were taken seriously by heavy-weight thinkers and writers and Janik argues that we should look afresh and without bias at what he actually proposed. He does an excellent job in this fairly short exploration of explaining Weininger's world-view and is, up to a point, an apologist for him. Nevertheless some of Weininger’s views are certainly problematic – for example that Jews should stop breeding and thus in one generation the Jewish “problem” would be solved. Janik makes his case well and I found this a fascinating examination of a deeply troubling and troubled thinker and agree that in spite of his negative reputation it is indeed worth looking at him objectively rather than with a knee-jerk reaction. I learnt a lot from this accessible and clearly written volume and it certainly deserves more reviews than it has so far garnered. (Feb 2022)