We talk about indexes with the author of the book “Index, a History of the,” Dennis Duncan, and its indexer, Paula Clarke Bain. Modern indexes date back eight centuries, and Dennis’s book takes us from the beginning to the present. Paula has worked for over 15 years as a professional indexer and produced nearly 900 indexes. She explains her working methods and the value of an index to the reader—and as an element of a book’s appeal.