In the winter of 1417, a short, genial, cannily alert man in his late thirties plucked a very old manuscript off a dusty shelf in a remote monastery, saw with excitement what he had discovered, and ordered that it be copied. He was Poggio Bracciolini, the greatest book hunter of the Renaissance. His discovery, Lucretius' ancient poem On the Nature of Things, had been almost entirely lost to history for more than a thousand years.
It was a...