Most of us give little thought to the back of the book—it’s just where you go to look things up. But here is the secret world of the index: an unsung but extraordinary everyday tool, with an illustrious but little-known history.

Charting its curious path from the monasteries and universities of thirteenth-century Europe to Silicon Valley in the twenty-first, Dennis Duncan reveals how the index has saved heretics from the stake, kept politicians from high office, and made us all into the readers we are today. We follow it through German print shops and Enlightenment coffee houses, novelists’ living rooms and university laboratories, encountering emperors and popes, philosophers and prime ministers, poets, librarians, and—of course—indexers along the way. Duncan reveals the vast role of the index in our evolving literary and intellectual culture, and he shows that in the Age of Search we are all index-rakers at heart.