Brad DeLong delivers a sweeping economic history of the “long twentieth century” (roughly 1870–2010), chronicling how humanity escaped centuries of Malthusian poverty through exponential technological and industrial innovation, dramatically raising living standards worldwide. Yet, despite this unprecedented material progress – what DeLong dubs a “slouch” toward utopia – the era ended not in a perfect society but one marked by persistent inequality, climate change, economic instability, and widespread dissatisfaction. Drawing on a rich political-economic narrative, he weaves together ideas from Keynes, Hayek, Polanyi, and others to explore how policy, ideology, and institutions shaped both the gains and the setbacks of this transformative age.