In 1874, John Richard Green, a virtually unknown former clergyman, sold the rights for his school textbook, A Short History of the English People, to Macmillan for 350 pounds sterling, a generous sum for a work expected to sell a few thousand copies. To everyone's astonishment, the work sold 32,000 copies in its first year, and a half million copies thereafter. This publishing phenomenon was also a breakthrough in historiography, for unlike...