At an ecopark in Mexico, tourists pretend to be illegal migrants, braving inhospitable terrain and the U.S. Border Patrol as they attempt to cross the border. At a living history museum in Indiana, daytime visitors return after dark to play fugitive slaves on the Underground Railroad. In the Mojave Desert, the U.S. Army simulates entire provinces of Iraq and Afghanistan, complete with bustling villages, insurgents, and Arabic-speaking townspeople, to train soldiers for deployment to the Middle East. At a nursing home, trainees put on fogged glasses and earplugs, thick bands around their finger joints, and sandbag harnesses to simulate the effects of aging and to gain empathy for their patients. These immersive environments in which spectator-participants engage in simulations of various kinds—or “simming”—are the subject of Scott Magelssen’s book. His book lays out the ways in which simming can provide efficacy and promote social change through affective, embodied testimony. Using methodology from theater history and performance studies (particularly as these fields intersect with cultural studies, communication, history, popular culture, and American studies), Magelssen explores the ways these representational practices produce, reify, or contest cultural and societal perceptions of identity.