Models are important to all we do. Whether we utilise them or are simply affected by them, they serve as metaphors for the increasingly complicated difficulties we face in the modern world. We couldn't begin to address three of modern society's key concerns without models: economic regulation, climate change, and the COVID-19 epidemic. However, the validity of the models we employ has been passionately disputed in recent years, and there has been growing awareness of the terrible effects when model designers and interpreters get things wrong. Erica Thompson investigates what models are, why we need them, how they work, and what happens when they fail, using modern examples from finance, climate, and health policy. This is not a book that suggests we should abandon models; rather, it argues that we need to understand how they are built - and how some of the assumptions that underpin the models we employ might have substantial unexpected implications. This is necessary reading for everyone since it is unexpectedly funny, thought-provoking, and impassioned.