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

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

But there’s no getting around that learning IS work. A superior non-fiction book organizes material so that the reader can learn efficiently and enjoyably. The book’s title and the table of contents certainly help orient the reader in this process. But it is the index which helps the reader quickly locate pertinent discussions of topics 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 of the digital version may result in dozens of irrelevant passing mentions. The index brings 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. The index is an essential learning tool that helps the reader assimilate the information in your book more efficiently, thus offering real value.