Everyone is passionate about something, but not all of us become fanatics. Why and how some people do is a fascinating question with both practical utility and broad implications for our social, emotional, physical, and financial wellbeing. Joe Ungemah explores the psychological motivations behind fanaticism through interviews and direct experience. Falling within the social, physical, cognitive, and emotive psychological domains, these motivations combine to make a particular passion core to someone's identity. The Social section introduces the power of shared experience and common fandom by profiling science fiction fanatics, as well as considering how some individuals cope with severe hardship and tragedy by throwing themselves into activism or social movements. The Physical section explores the extreme opposites of ultramarathon runners who completely immerse themselves in physical exhaustion and gamers who pursue escapism with the therapeutic and commercial applications of VR. The Cognitive section considers obsessive behaviors and their motivations through the contrasting experiences of collecting and hoarding, as well as the world of innovation and entrepreneurialism. The final section, the Emotive, takes a ride through the world of thrill seekers with roller coaster enthusiasts and extreme sports, and the reward feedback that results from impulse buying. This exploration of fanaticism demystifies the concept and recognizes the benefits it provides. With nearly an unlimited range of topics that could seed fanaticism, Fanatic argues both that we all have the potential to become a fanatic, and that fanaticism should be embraced for its work in creating a sense of purpose and identity, as well as the opportunity for connection it provides.