What Is a Book Index and Why Is It Important?

POSTED ON Nov 18, 2021

The Book Designer

Written by The Book Designer

Home > Blog > Writing > What Is a Book Index and Why Is It Important?

What is an index? If you’ve ever read a book in your life (which we hope you have) you’ve come across and used an index. The exact definition is, “an alphabetical list of names, subjects, etc., with references to the places where they occur, typically found at the end of a book.” If you crack open almost any non-fiction book, you can find one.

It’s one of those parts of a book that are easily overlooked for how helpful it is until you need it. If you’ve ever had to look up something in a book, you appreciate when an index is properly done.

The last thing you ever want is for your readers to go to your index and not find something that clearly should have been labeled and categorized, or worse, in the wrong place. It’s a small part of the book, but it is constantly used so you want to make sure you’re spending the time to do it right.

What is an Index?

Typically, it’s a collection of categories that point the reader back to certain page numbers to find more information about that particular topic. They are also used in databases online to categorize and organize information to group it together. That’s just something to keep in mind for any digital versions of your book you might make.

For example, if you’re creating a recipe book, you could group all of your recipes together that use chicken.

Indexes are different from tables of contents. Tables of contents describe what each chapter contains and how the book is laid out whereas the index groups categories together throughout the whole book.

This article will go over some of the basics you need to know about indexes and how to put one together.

what is a book index - big research library
Putting together an index will seem daunting. Don’t worry though — one term at a time, or as Anne Lamott would say, “bird by bird”!
New call-to-action

Putting Together Your Index

The first thing you need to know is that all indexes are alphabetical. That gives you at least a starting framework of placing and organizing your categories.

As you start to list out the keywords and topics that are included in your book, you’ll want to avoid using every single nuanced description and instead try to keep things broad if possible.

Going back to the earlier example about the cookbook, unless you have hundreds of egg recipes, you’ll just want to categorize that as “eggs” instead of “fried eggs, over easy eggs, hard boiled eggs” and so on. Otherwise, you’re going to end up with an index that is longer than the whole book.

Only make sub-categories when it’s important and related to the topic of your book or helps break up a large chunk of long page references.

Some books also need an index for any authors, studies, or work cited. Depending on the type of book you’re writing, you might also need to place your references throughout the book, but you will at the very least need to put them in the back of your book.

Pulling Out Your Keywords and Categories

Putting together your list of indexed words and categories is one of the hardest steps to creating an index.

You’ll want to ask questions such as: 

  • What should you focus on?
  • What will people need to back and look for?
  • What things do you talk about throughout the book?

One place to start is to think about each chapter and ask yourself what are the main things each chapter is covering. For every main topic you cover, you’re going to write that down in your index draft.

If you haven’t read through each page of your book in some time, you should carve out time to at least briefly read through it to remember what each part covers.

Depending on how people use words in your industry, you might want to use alternative or slang for some words. Of course, you don’t want to use every alternative word possible because it could make your index way too long. At the same time, you want to make sure your book is accessible to everyone so it shouldn’t contain too much industry-only language, either.

Some authors use index cards as they’re going through their book to keep track of their pages and reference points, compared to only using computers to do the whole process. Some also prefer to use page markers to indicate certain sections or topics.

Keep in mind, if your book hasn’t gone through any rounds of heavy editing, chapters and pages are most likely going to change. In that case, you might want to keep your indexing loose compared to a strict page number.

Formatting Your Index

When it comes to formatting your index, thankfully most word processors have some type of template or other options to start creating your index. However, if you want your index formatted correctly, there are a few things you need to keep in mind.

Once you decide on a basic formatting style, you’ll want to stay consistent as you go through and write your index. If you have a publisher, they might have a format they prefer to use.

Most writing processors, even with built-in indexing, don’t always translate to the published version. Some publishing companies even have professional indexers to make sure every page matches the exact index page counter.

You’ll want to start every index word with a noun. Going back to the earlier example, you shouldn’t list hard boiled eggs as “hard boiled eggs”, instead you’d categorize it under “eggs, hardboiled”. This is something you should keep in mind as you go through your book to see if there are certain areas you can group together.

If you’re referencing a publication, you’ll need to make that italic. (Keep that in mind for both the index and the references page.)

Almost all entries in an index are not capitalized. The only exception is for titles or names.

New call-to-action

Editing Your Index

Now that you’ve put in the hours to compile everything into one place, now is the time to go through and edit your index. Not only do you need to make sure that the entries are correct, but you also need to make sure there aren’t any typos.

If you are using names or titles of things, you’ll need to make sure the spelling is consistent and correct, even if your spell check software doesn’t catch it. For example, if you are quoting a researcher named John Grey, but in the index you call him John Gray, your autocorrect will not catch the difference.

Thanks to modern computers, you can now search for keywords throughout your texts to make sure you don’t miss anything, if needed.

If you have a publisher, you will have help when it comes to putting your index together. If you’re doing it yourself, just know it can take a long time but it will be worth it once it’s done.

For anyone who has access to beta readers, it might be worth it to see if they have any input on your index. They might have some ideas of topics they wanted to look up but couldn’t find in the index.

You’ll want to do a deep-dive into your book to make sure you’re not indexing parts that are no longer there or were removed during one of the editing phases. If you are using writing software with a built-in index, it should catch that these parts or words have been removed, but be sure to manually check each one.

Either way, be sure to go through the entire index thoroughly because once your book goes to print, you cannot undo any mistakes.


Your index might seem like an after-thought as you’re creating your book, but it will be something your readers will often refer to again and again. Everyone in the future who reads your book will appreciate the hard work that went into grouping everything together every single time they need to look something up.

The Book Designer

Written by
The Book Designer

Liked this post? Share it with friends!

More Helpful Articles