About Indexes and Indexing: Why Do We Need an Index?

Books are about discovery, whether it’s discovering a new world of fiction created in the imagination of the author, or learning about the astrophysics that allows the Curiosity rover to explore the surface of the planet Mars. While fiction is generally focused on the reader’s enjoyment, the focus of non-fiction is learning. Not that learning isn’t enjoyable. In fact, learning can be extremely satisfying when readers feel they’re making progress and assimilating the material successfully. They’re “discovering” something new.

But there’s no getting around that learning IS work. A good non-fiction book organizes material in such a way that the reader can learn efficiently and enjoyably. The index, along with the book’s title and the table of contents, can help the reader quickly locate pertinent discussions of a topic of interest. For example, in a book on engineering, a reader may be interested in the concept of "angular momentum." This topic may or may not be represented in the table of contents, and a search in the ebook version may result in dozens of irrelevant passing mentions. The index will bring together, under one index heading and organized by subtopic, all pertinent discussions and mentions of angular momentum that come up in the book. The index may also help the reader by suggesting other, related, terms, such as "spin."

Readers use indexes in different ways. For example, a reader wants to see where in the book a certain topic is covered, and they “look it up” in the index. But a reader may also want to get an in-depth overview of the book’s contents, and the index also provides that. An index not only lists all of the pertinent terms, for the more important terms, it puts them in context with the help of subheadings. A well-constructed index will provide the proper balance of specific terms and general concepts, broken down into more specific subheadings where appropriate.

The index makes learning, and hence discovery, easier and more efficient for the reader. It is an essential feature that helps the book provide more value to your readers.