Codex AI Book Writer vs ChatGPT: Which Should You Use to Write a Book?
Published 31 October 2026. 3 min read.
Most people who want to write a book with AI already have ChatGPT. So the fair question is: why use anything else? This page answers it honestly, including where ChatGPT is the better choice.
The short answer
ChatGPT is a general assistant. You can write a book with it, but you are the one holding the book together: you keep the outline, ask for each chapter, remind it what came before, and copy the text out piece by piece. Codex AI Book Writer does one job. It plans the whole book as an outline you approve, writes every chapter to that plan, keeps every version and hands you finished files.
Side by side
| Codex AI Book Writer | ChatGPT | |
|---|---|---|
| Planning the book | A chapter-by-chapter outline with word counts. You rewrite or delete parts before anything is written. | You ask for an outline in the chat and keep track of it yourself. |
| Writing the chapters | Every chapter is written from the approved outline in one run, usually in a few minutes. | One reply at a time. Long books need many prompts, and earlier chapters can drift out of view. |
| Rewriting | Regenerate any chapter with a new instruction. Every version is kept, so you can switch back. | Ask again in the chat. Earlier answers stay in the conversation, not in the book. |
| Finished files | PDF, Word (DOCX), EPUB and a web page (HTML), with your cover, author name and publisher. | Text in a chat window. You assemble and format the book yourself. |
| Your books | Kept in a library in your account, ready to re-download. | Spread across conversations. |
| Price | 10,000 free tokens, then packs of 10,000 for $5.99, 30,000 for $14.99 or 100,000 for $29.99. No subscription; tokens never expire. | A free plan with limits; paid plans are monthly subscriptions. |
| Best for | Turning one idea into a structured non-fiction draft you can edit and publish. | Brainstorming, research questions, short pieces, and anything that is not a whole book. |
What a real book costs in Codex AI Book Writer
In English a word costs about 1.3 tokens. A 20,000-word guide comes to about 26,000 tokens, which fits in one $14.99 pack with some to spare. A 50,000-word book is about 65,000 tokens, inside one $29.99 pack. Rewriting a chapter uses tokens again, so leave room for that. You always see the estimated cost before a book is written, and if your balance runs out, writing pauses and carries on when you top up.
Every new account starts with 10,000 tokens, enough for a short book before you pay anything.
When ChatGPT is the better choice
- You want to talk an idea through before you know what the book is.
- You are writing something short: an article, a blurb, a single chapter.
- You already pay for it and are happy to assemble and format the book yourself.
Plenty of authors use both: ChatGPT to think, Codex AI Book Writer to build the book.
Publishing on Amazon KDP
Whichever tool writes the draft, Amazon asks whether AI generated any of the text, images or translations, and a book drafted by AI counts as AI-generated even after you edit it. Answer yes. We explain the rules in Publishing an AI-Written Book on Amazon KDP.
Try it with your own idea
Describe your book in two sentences and look at the outline before you decide anything. Start writing free.