An index is an alphabetical list of important topics, names, concepts, and other terms mentioned in your book, together with the page numbers where readers can find them. It is usually placed at the very end of the book, after the main chapters and other end matter.

The purpose of an index is to help readers locate specific information quickly without having to browse through the entire book. This is particularly useful for nonfiction books that cover several topics, introduce specialist concepts, or are intended to be used as a reference over time.

Unlike a table of contents, which shows the structure of your book chapter by chapter, an index helps readers find specific information within those chapters.

What Should You Include in an Index?

An index should focus on information that readers are likely to search for when returning to your book. Depending on your subject, this might include:

  • Key Topics: Important subjects and themes discussed throughout the book.
  • Concepts and Ideas: Principles, theories, methods, and frameworks introduced in your chapters.
  • People and Organizations: Names of important individuals, companies, institutions, or other organizations.
  • Technical Terms: Specialist terminology and industry-specific expressions.
  • Methods and Processes: Particular techniques, strategies, or approaches explained in the book.
  • Important Examples: Significant case studies or examples that readers may want to revisit.

For example, an index in a book about leadership might include entries such as communication, delegation, employee motivation, emotional intelligence, and performance management. Think about the topics your readers are most likely to look up after finishing the book. Those are the entries worth considering.

How to Organize Your Index

The standard approach is to organize index entries alphabetically, making them easy to scan and locate. Each entry should include the relevant page number or page numbers. For example:

Communication, 18, 42–45, 87

Delegation, 56–59, 112

Employee motivation, 34, 78–81

You can also use subentries when a topic covers several related subjects. For example:

Communication

  • active listening, 42–43
  • feedback, 44–45
  • workplace communication, 87–89

Subentries help readers narrow down their search and find the specific information they need. You should also think carefully about the wording of your entries. Use terms that readers are likely to search for, rather than simply copying every heading from your chapters.

What Should You Watch Out For?

Creating a useful index requires more than collecting words and adding page numbers. Keep the following points in mind:

Don't index everything. Focus on meaningful topics and concepts that readers may want to find again. Common words and passing references usually do not need their own entries.

Use consistent terminology. If you refer to the same concept using different expressions, consider grouping them under one main entry or including cross-references where appropriate.

Make page references accurate. Page numbers must correspond to the final version of your book. This means the index should normally be prepared after the manuscript has been designed and the page layout is finalized.

Avoid overly broad entries. If a topic appears on many pages, use subentries to help readers find the relevant discussion rather than providing a long list of page numbers without context.

Include cross-references where useful. These direct readers from one entry to another. For example, an entry might say "See also Employee engagement" to help readers discover related information.

Check the finished index carefully. Review the page references, spelling, alphabetical order, and consistency. Even a well-organized index becomes frustrating if the page numbers are incorrect.

When Does Your Book Need an Index?

Not every nonfiction book needs an index. It is particularly useful for reference books, professional guides, textbooks, technical publications, and books that cover a wide range of subjects. If readers are likely to return to your book to find specific information, an index can significantly improve its usefulness. For a short, straightforward book that readers are expected to read from beginning to end, an index may not be necessary. A clear table of contents may be sufficient. Consider how your audience will use the book. If it is something they may keep on their desk, consult during their work, or revisit when they need advice, an index is often a worthwhile addition.

When Should You Create the Index?

An important consideration is timing. Unlike most other elements of your end matter, an index should generally be created after the book's interior layout has been finalized. This is because the index depends on accurate page numbers. If you create it before the manuscript has been typeset, later changes to the layout can shift the page references and make the index incorrect. Many professional book designers and publishers use dedicated indexing tools or work with an indexer to prepare the final version. Some book layout applications also offer indexing features. AI can help you identify potential index terms and organize them alphabetically, but you should not rely on AI alone to generate accurate page references. These need to be checked against the final, paginated book.

Final Thoughts

An index is a practical feature that makes a nonfiction book easier to navigate and use as a reference. It helps readers find important topics, concepts, and information without having to search through the chapters themselves. You don't need an index for every book, but if your readers are likely to revisit specific sections, it can add considerable value. Plan the topics and terms you want to include while writing and editing your manuscript, but create the final index only once the book's page layout is complete. That way, your page references will be accurate and your readers will be able to find exactly what they are looking for.