Otto Weininger’s Sex and Character became one of the most notorious books of fin-de-siècle Vienna. Published two years after Weininger’s suicide, Emil Lucka’s Otto Weininger: His Work and Personality is one of the earliest attempts to explain the man and the system behind the scandal. Lucka writes as someone who knew Weininger personally, read the work in its formation, and discussed its central problems with him. He does not offer a neutral academic summary. He presents Weininger as a philosopher of value, ethics, sex, character, genius, Judaism, Christianity, culture, and metaphysics, while also correcting hostile misunderstandings and crude attempts to dismiss him as insane. The book follows Weininger through biology, bisexuality, sexual intermediate forms, male and female psychology, characterology, Kantian ethics, genius, the ego, love, sexuality, and the problem of value. The appendix by Leopold Weininger, the author’s father, replies to Ferdinand Probst’s The Case of Otto Weininger and corrects biographical distortions. This is an essential early document in the reception of Weininger and the intellectual atmosphere around Sex and Character.