Donald MacKenzie explores a provocative thesis: financial economics didn't just describe markets—it transformed them. Drawing on detailed historical research, MacKenzie shows how the Black-Scholes option pricing model moved from academic journals to trading floors, and in doing so, changed how options were priced. Before the model, option prices varied widely; after traders adopted it, prices converged toward its predictions. MacKenzie frames this as finance theory functioning as an 'engine' that shapes markets, not merely a 'camera' that records them. He traces how theoretical concepts gave legitimacy to financial instruments previously viewed with suspicion. Derivatives markets exploded in part because theories explained their value and proper pricing. The book examines both the successes and failures of this performativity. When market conditions diverged from model assumptions, as in the 1987 crash and the 1998 Long-Term Capital Management crisis, theory's limits became painfully apparent. MacKenzie, a sociologist of science at Edinburgh, brings rigor to questions about how knowledge shapes the reality it claims to describe. For anyone seeking to understand modern finance's intellectual foundations and their real-world consequences, this remains an essential work.