The first English-language monograph on Hermann Broch's literary and theoretical work on mass hysteria. Austrian Jewish author Hermann Broch (1886-1951), a leading figure of European Modernism, spent decades attempting to understand the phenomenon of mass hysteria. With his work, he hoped to help protect society from the allure of mass hysteria, embodied in the fanatical appeal of National Socialism. He was torn between two approaches to the problem: using literature to diagnose and expose the irrational knowledge that underpins mass hysteria, and employing theory as a more precise and effective means of doing the same. In this first English-language monograph on the topic, Brett E. Sterling traces the development of Broch's understanding of the mass from an initial confrontation in 1918 to a recurring theme in his fiction and ultimately to the monumental but incomplete Massenwahntheorie (Theory of Mass Hysteria, 1939-48). In thorough readings of Broch's major fictional and theoretical works, the analysis centers on the question of how his literature and theory provide distinct but complementary approaches to conceiving and representing the elusive figure of the mass and the attendant experience of mass hysteria. With political extremism and conspiratorial thinking on the rise, Sterling makes the case that Broch's insights into mass hysteria - literary as well as theoretical - are of renewed relevance to a contemporary audience.