In the days when Columbus sailed the ocean and Da Vinci painted the Mona Lisa, a German banker named Jacob Fugger became the richest man in history. Fugger lived in Germany at the turn of the sixteenth century, the grandson of a peasant. By the time he died, his fortune amounted to nearly two percent of European GDP. In an era when kings had unlimited power, Fugger dared to stare down heads of state and ask them to pay back their loans—with interest. It was this coolness and self-assurance, along with his inexhaustible ambition, that made him not only the richest man ever, but a force of history as well. Before Fugger came along it was illegal under church law to charge...