The General Theory of Employment, Interest, and Money

The level of employment, in the theory John Maynard Keynes lays out here, is set by aggregate demand rather than by the price of labour. The English economist rejected the classical view that competitive markets settle at full employment unaided, and argued that the unstable psychology of markets brings periodic booms and crises. It introduced liquidity preference, the consumption function and the principle of effective demand, and gave fresh prominence to the multiplier and to the marginal efficiency of capital. It put macroeconomics at the center of economic theory and was read as backing government spending, deficits and counter-cyclical policy. In a letter to George Bernard Shaw, Keynes predicted it would change how the world thinks about economic problems.

Eric Weinstein, managing director at Thiel Capital, shared it on Twitter among the books that mattered enough to him to bring home when he cleared out an office.