It has become a truism that the economic system of the Soviet Bloc failed, but the actual record of accomplishments and disappointments is much more nuanced. State socialism did not bring the grand achievements that its founders had hoped for, but neither did it leave these countries significantly worse off, in relative terms. In fact, most Soviet countries did better overall under socialism than under capitalism. Once we recognize this, we face a puzzle: why did so many economists within the Soviet Bloc come to believe that they were working within a catastrophically dysfunctional economic system? And why, when presented with a crisis in the late 1980s, were they so quick to push their countries towards capitalism? Brian Porter-Szucs answers these questions by telling a story about the triumph of neoclassical economics that transcends the Soviet Bloc. Drawing on the writings of policymakers, planners, university professors, economic journalists, and others who were trying to put Marxist ideals into practice, he shows how market socialists embraced the methodological principles of their capitalist counterparts but argued that these could be applied just as well to socialist forms of property ownership. Opponents of this approach on the left countered that market exchange invariably leads to the commodification of everything, including human labor, which in turn introduces a systemic logic that reproduces forms of exploitation indistinguishable from capitalism. That prophecy, Porter-Szucs argues, was correct. Policymakers and economic advisors pushed Poland towards market mechanisms that fundamentally undermined the original socialist project, and in doing so they generated considerable popular discontent. The final crisis of the 1980s resulted from a combination of bad decisions and bad luck, and the authorities dealt with these by pursuing an austerity agenda that only generated more opposition, ultimately leading to the dramatic collapse of communism, not just in Poland but across Eastern Europe in 1989.