Bill Gates is many things: the richest person in the world; the ruthless businessman who co-founded Microsoft and led it to domination of the computer software industry; and now, the leading global philanthropist. When Gates was born in 1955, no one in the world owned a personal computer. A window had a pane of glass. A mouse was a rodent. As a teenager, Gates realized how computers were about to change the world, and made his fortune by riding that wave; modern teens look to him as their model of how technology can be turned into wealth. Marc Aronson’s biography is a probing portrait of a man whose name is a household word.