The index, tucked away in the back of a book, is often overlooked. But after reading Dennis Duncan’s delightful history of the tool, you’ll never forget to check the index again. In Index: A History of the: A Bookish Adventure from Medieval Manuscripts to the Digital Age, Duncan traces the index’s 800-year history, from medieval monasteries and universities to its uses for the tech boom in the present day. In doing so, he makes a case that indexes have not only impacted our literary and intellectual culture, but also shaped the way we communicate and engage with power. They might even have saved lives along the way. —Cady Lang