You finished writing your nonfiction book. You formatted it, got the cover designed, and you're staring at the production checklist. Then you see it: index.
And the question lands: do I actually need one?
The honest answer isn't a flat yes or no — it depends on your book type, your page count, and who your readers are. But for most nonfiction authors publishing a 100+ page book on Amazon or through any retailer, skipping the index is a quiet mistake that costs you more than you'd expect.
Here's how to decide.
The Types of Nonfiction That Almost Always Need an Index
Not every nonfiction book needs an index, but certain categories effectively require one if you want to be taken seriously by readers and reviewers.
Reference books and guides are the clearest case. If readers will return to your book repeatedly — looking up a specific term, finding a chapter they remember but can't locate, checking a fact — an index is the navigation system that makes the book genuinely useful over time. Without it, readers flip through pages hoping to find something they remember seeing. With it, they go directly to what they need. That difference matters to how readers rate and recommend your book.
Business books, leadership titles, and professional development books are the second clear category. Your reader bought this book because they want to apply the ideas. When they're six months post-reading and trying to locate your three-step framework or the case study about the company they found compelling — they'll use the index. If it doesn't exist, many will simply give up and find another source.
History, biography, and narrative nonfiction sit in the middle. Academic presses typically require indexes for these. Trade publishers usually include them for 200+ page works. As a self-published author, the practical rule is this: if readers will search your book by a person's name, an event, or a specific topic, they expect an index.
When You Can Reasonably Skip It
Not every nonfiction title needs a full back-of-book index. Shorter books — under 100 pages — rarely benefit from one. The effort exceeds the payoff when readers can scan the whole text in under an hour.
Narrative-heavy books where readers engage cover to cover rather than dipping in and out are also candidates for skipping. A memoir told in strict chronological order, a personal essay collection, a short inspirational title — readers follow the through-line rather than searching for specific content.
Ebooks without print editions are a special case. Traditional indexes rely on fixed page numbers from a typeset PDF. Ebook readers can search full text natively, which reduces — but doesn't eliminate — the value of a structured index. If you're publishing print and ebook simultaneously, build the index for print; it adds credibility to both editions.
The Decision Framework: Four Questions
If you're still unsure, run your book through these four questions:
1. Is it 100 or more pages? If yes, you're in index territory. The industry standard — from professional indexers, library catalogers, and major publishers — treats 100 pages as the threshold where a back-of-book index becomes expected.
2. Will readers search it, not just read it? A book someone reads once for inspiration is different from a book someone consults repeatedly for guidance. If your readers are likely to say "I know this book covers X — I just need to find where," an index turns a good book into an indispensable one.
3. Does your book contain proper nouns worth locating? People, organisations, places, frameworks with specific names — these are exactly what indexes surface. If your book references fifteen research studies, five industry leaders, and a dozen named methodologies, an index isn't optional. It's how readers find the thing they half-remember from chapter eight.
4. Would a missing index embarrass you in a review? This is the most direct question. Professional reviewers, librarians, and experienced nonfiction readers notice the absence of an index in books where one is expected. "Well-written but lacks an index" is a real line in real reviews. It's an avoidable criticism.
What Skipping an Index Actually Costs You
The cost isn't just reader experience. It's credibility.
Readers who buy nonfiction with the intention of using it — applying it, referencing it, keeping it on their shelf — use the index to evaluate whether the book is serious. Browsing an index before buying is a legitimate purchase signal. Some readers, particularly those who've been burned by shallow business books, go straight to the index to confirm depth.
There's also the professional review channel. Library acquisitions, academic reading lists, and editorial reviews for trade nonfiction routinely treat an index as a sign of a book produced to professional standards. It signals that the author understood readers would want to find specific content — and made that possible.
Against all of that: professional indexers charge $4–$8 per indexable page, which means a 250-page nonfiction book typically runs $1,000–$2,000. That figure stops a lot of indie authors cold. The timing problem compounds it: indexers require your final, typeset PDF before they can begin, which compresses your production timeline right when it's already tight.
The cost-and-time barrier is real. It's also no longer the only option.
The Bottom Line
If your nonfiction book is 100+ pages, covers a substantive topic that readers will return to, and contains concepts or names worth locating — you need an index. That's most nonfiction books that aren't short, narrative, or purely inspirational reads.
The question isn't whether to have one. It's how to get one efficiently, at a production stage when your timeline and budget are already stretched.
Onomastic was built for exactly this moment in the publishing workflow. Upload your final typeset PDF, and get a CMOS-compliant index — complete entries, subentries, and cross-references — in under two hours. Authors who assumed indexing was out of their budget or timeline find it's neither.
The index your book needs doesn't have to be the thing that delays it.
