The Best AI for Writing a Book in 2026 (Fiction and Non-Fiction)

The best AI for writing a book depends on what you want the AI to do. If you want it to help you plan, track canon and draft on your own terms, pick Novelcrafter. If you want fast, fiction-tuned prose help built into one subscription, pick Sudowrite. If you already have a draft (fiction or non-fiction) and want feedback and line editing, pick ProWritingAid.

Our angle at writingforu.com is simple: use AI as an assistant, not a ghostwriter. That's the safer path for your voice, for publishing-platform rules, and for copyright. A note on method: this roundup is built from vendor documentation, pricing pages and published reviews, not from our own hands-on testing. Where sources disagreed, we say so.

Quick picks

• Best overall for fiction authors who want control: Novelcrafter. The planning tools work without AI, and you choose and pay for the model yourself.
• Best for drafting and rewriting fiction: Sudowrite. A fiction-focused model, a Story Bible and tools like Write and Draft in one place.
• Best for editing a finished draft (fiction or non-fiction): ProWritingAid. Style reports and chapter feedback, with a lifetime license option.
• Best for non-fiction authors: ProWritingAid, because the other two are built around novels.
• Best for staying clear of KDP disclosure: ProWritingAid, or Novelcrafter used for planning only.

Comparison table

Tool	Best for	Price	Platforms	Free trial
Sudowrite	Drafting and rewriting fiction	from $10/month billed yearly, $19 monthly (as of October 2026)	Web; iOS and Android companion apps	Yes, no card needed; no permanent free plan
Novelcrafter	Planning novels and series, optional AI	from $4/month (no AI); AI from $8/month plus your own AI provider costs (as of October 2026)	Web	21 days
ProWritingAid	Editing and feedback on a finished draft	from $10/month billed yearly ($120/year), $30 monthly (as of August 2026)	Web editor, browser, Word, Google Docs, Scrivener	Free plan limited to 500 words per check

Prices are in US dollars and can vary by plan and billing period.

1. Sudowrite: best for drafting and rewriting fiction

What it is

Sudowrite is built around Muse, a proprietary model trained on fiction, plus a Story Bible that keeps the AI aligned with your characters, worldbuilding and style. It's a fiction tool first. If you write memoir or business books, you're not the target reader.

Who it is for

Novelists who get stuck mid-scene, write thin first drafts, or want rewrite options on tap. It also suits writers who like a single subscription over assembling their own AI setup. Our Sudowrite review goes deeper on fiction use.

Key features

• Write: Before it writes anything, Write reads your preceding story plus your Story Bible. Auto mode continues, Guided mode lets you steer what happens next.
• Draft: Once your Story Bible has an outline and scenes, Draft turns a scene into prose.
• Rewrite, Expand, Describe and Brainstorm: smaller tools for reshaping tone, slowing a rushed scene, adding sensory detail and generating ideas.

Pricing

As of October 2026, Hobby & Student is $10 a month billed yearly or $19 monthly, Professional is $22 or $29, and Max is $44 or $59. Features are the same across tiers; what changes is the credit allowance. On Hobby and Professional, unused credits vanish each billing month, and only Max carries a balance forward, for up to 12 months.

One snag: Sudowrite's documentation lists 1,000,000 monthly credits for Professional, but some sources list 450,000, so confirm the allowance at checkout.

There's a free trial but no free plan you can keep using. Third-party reviews report a one-time trial of roughly 10,000 credits.

Pros

• Built for fiction, with a Story Bible and scene-to-prose workflow in one editor
• Tools cover the whole drafting cycle, from brainstorming to rewriting
• No API keys or model setup
• Works on web, with iOS and Android companion apps that have fewer features than the web editor

Cons

• Credit-metered pricing is hard to predict, and heavy use of the premium model can burn through allowances fast
• If you cancel or your trial ends, you keep your projects but lose the AI features
• Write and Draft generate prose, which triggers KDP disclosure if that text stays in your book (more below)
• Not designed for non-fiction

Choose it if you write novels or short stories and want an AI partner that sits inside your manuscript.

Skip it if you want AI nowhere near your prose, you write non-fiction, or you hate metered credits.

Try Sudowrite free

2. Novelcrafter: best for planning novels with optional AI

What it is

Novelcrafter is a browser-based novel-writing app where AI is an add-on. The AI is optional, not the core. The core is the editor, scene structure and the Codex, a wiki for characters, places and lore.

Who it is for

Plotters, series writers and anyone who wants to pick their own model. It also suits writers who want a story bible and no AI at all. If you're torn between this and Sudowrite, read our Sudowrite vs Novelcrafter comparison.

Key features

• Codex: It acts like a personal Wikipedia for your characters, worldbuilding and plot points.
• Bring your own key (BYOK): Novelcrafter has no built-in credits system, so you connect your own AI provider. OpenRouter is the common route, and free local models through Ollama or LM Studio work from the Hobbyist tier up.
• AI tools on Hobbyist: Scene summarization, character extraction and generating from scene beats; Workshop Chat is a higher-tier feature.
• Scale: the Scribe plan includes unlimited books and series.

Pricing

Plans are Scribe at $4 a month, Hobbyist at $8, Artisan at $14 and Specialist at $20; paying yearly costs $40, $80, $140 and $200. Prices are as of October 2026. Scribe has no AI at all, not even the option to connect your own key.

So the real cost is plan plus provider. Provider costs run from $0 on free models to several dollars a month at steady use on a mid-priced model, and more for heavy premium use. There's no permanent free plan, but the 21-day trial unlocks all features with no credit card.

Pros

• Planning and organization work well even with AI switched off
• You choose the model and see exactly what you spend
• Local models keep drafts off third-party servers
• Cheap entry price compared with credit-based tools

Cons

• Setup means creating a provider account, generating an API key and pasting it in. Reviewers describe this setup as technical.
• You choose which scenes and Codex entries the AI sees as context, which takes some effort
• Web-only, so no offline app (check the current site if that matters to you)
• AI spend sits outside the subscription

Choose it if you like systems, write series, and want AI as a tool you control.

Skip it if you want one-click drafting with no configuration, or you'd rather not manage API keys.

Start the Novelcrafter trial

3. ProWritingAid: best for editing a finished draft

What it is

ProWritingAid is a grammar and style editor aimed at long-form writers. It checks prose you've already written and gives feedback. That makes it the least risky of the three from a disclosure standpoint, and the only one that fits a non-fiction manuscript without much fuss.

Who it is for

Authors with a draft who want line-level cleanup and chapter-level feedback. It integrates with Word, Google Docs, Scrivener and web browsers. If you're weighing it against a mainstream rival, see ProWritingAid vs Grammarly.

Key features

• 25+ writing reports: Echoes flags repeated words, Sticky Sentences catches filler-heavy lines, and Pacing highlights slow stretches of backstory and introspection.
• Chapter Critique and Sparks: Premium includes unlimited Rephrases, 1 Critique per day and 5 Sparks per day.
• Story Credits: Manuscript Analysis, Plot Analysis, Virtual Beta Reader and Marketability Analysis each cost 1 credit per run.
• Privacy: The company states it never trains its algorithms on user writing.

Pricing

Premium is $30 a month or $120 a year ($10 a month); Premium Pro is $36 monthly or $144 yearly; lifetime licenses are $399 for Premium and $699 for Premium Pro. Those are as of August 2026, based on published pricing guides, so check the live pricing page. The free plan only gives suggestions on 500 words at a time.

Watch the extras. No subscription includes Story Credits, so whole-manuscript reports are a second bill.

Pros

• Deep style reports that suit fiction and non-fiction alike
• Lifetime license option for writers who dislike subscriptions
• Works inside the editors you probably already use
• Feedback tools don't write your book for you

Cons

• Whole-manuscript analysis costs extra through Story Credits
• Monthly billing is expensive next to yearly
• Not a drafting tool, so it won't help with a blank page
• The free plan's 500-word cap makes it a demo

Choose it if you have a draft and want to tighten it, especially non-fiction.

Skip it if you want AI to generate scenes or chapters.

Try ProWritingAid

Where each tool sits on the "assistant vs ghostwriter" line

This is the practical test: does AI-written text end up on the page of your published book?

• Sudowrite's Draft and Write: these generate prose. If that prose lands in your book, you're in "AI-generated" territory, even if you rewrite it.
• Novelcrafter: depends on how you use it. Codex, outlining and brainstorming are assistance. Generating prose from scene beats is generation.
• ProWritingAid: mostly assistance. Reports and critiques give feedback on your text. Rephrase and Sparks can produce wording, so use judgment about what you paste in.

A general chatbot such as ChatGPT or Claude can do much of the same brainstorming and feedback work. The fiction tools above add a story bible and context management, which matter more as a manuscript grows. For more writing apps beyond AI, see our guide to the best writing software for authors, or browse the AI tools category.

What KDP and other platforms require

Amazon KDP's rule is about content, not tools. If AI created your content, you must tell Amazon; if AI only helped you refine content you created, you don't. KDP asks about AI-generated text, images (including the cover) and translations.

Three details trip people up:

• Heavy editing doesn't reclassify. Amazon's guidelines specifically state that substantial edits don't turn AI-generated content into AI-assisted content.
• Brainstorming and grammar help are fine. Content you wrote yourself and then improved with editing, error-checking, brainstorming or grammar tools counts as AI-assisted and needs no disclosure.
• The disclosure is private. It's internal to Amazon and isn't shown on your product page.

Don't skip the checkbox. Undisclosed AI content that Amazon discovers risks the book being blocked or removed, and patterns of it risk your account. These points come from summaries of Amazon's guidelines, so check the current KDP Content Guidelines before you publish. Other retailers and distributors set their own rules, and we haven't verified those here. Our self-publishing guide covers the full publishing workflow.

If you're ever accused of using AI when you didn't, keep drafts and version history. Our guide on how to prove you didn't use AI explains what evidence helps.

Copyright basics for AI-assisted books

This is general information, not legal advice, and the rules differ outside the US.

The US Copyright Office's January 2025 report is the best starting point. It concludes AI outputs can be protected only where a human author has determined sufficient expressive elements. That can include human-authored work visible in the output, or creative arrangement or modification, but not the mere provision of prompts. It also confirms that using AI to assist creation, or including AI material in a larger human-made work, doesn't bar copyright.

In plain terms: the more of the sentences you write yourself, the stronger your claim. A book that's mostly raw AI output may have little or nothing to protect. Separately, the D.C. Circuit has affirmed that human authorship is a bedrock requirement for registering a copyright.

If you want a public signal, the Authors Guild runs a Human Authored certification. Non-members pay $10 per title; it's free for Guild members. AI spelling and grammar tools are excepted, and using AI for research, brainstorming or outlining doesn't disqualify a title. Jane Friedman has criticized it because the Guild takes the author's word instead of analyzing the manuscript for AI use.

How to choose the best AI for writing a book

Start with what you want AI to do, then work backward.

1. If you want no AI in your prose: use ProWritingAid for editing and feedback, or Novelcrafter's Scribe plan for organization. Brainstorm with a chatbot if you like.
2. If you want help drafting fiction: pick Sudowrite for convenience or Novelcrafter for control. Plan to disclose on KDP if generated text stays in the book.
3. If you write non-fiction: none of these three is built for it. ProWritingAid is the practical choice, with a general chatbot for outlines and research prompts. Verify every fact yourself.
4. Check your budget model: Sudowrite is credits, Novelcrafter is plan plus provider fees, ProWritingAid is a subscription or lifetime license plus optional Story Credits.
5. Check your tolerance for setup: Novelcrafter rewards patience, Sudowrite is plug and play.
6. Test before paying: use Sudowrite's trial, Novelcrafter's 21 days, and ProWritingAid's free plan on a real chapter.

Whatever you pick, keep your voice in charge. Use AI to find the next beat, name the problem in a chapter, or cut repeated words. Write the sentences that carry your book.

FAQ

What is the best AI for writing a book?

It depends on the job. Novelcrafter suits planning and controlled AI use, Sudowrite suits fiction drafting, and ProWritingAid suits editing a finished draft. For most authors who want an assistant, not a ghostwriter, we'd start with Novelcrafter for fiction, because you control the model and the planning tools work without AI, and ProWritingAid for non-fiction.

Do I have to disclose AI use on Amazon KDP?

Only for AI-generated text, images or translations. Per summaries of Amazon's guidelines, using AI to brainstorm, edit or error-check content you wrote doesn't require disclosure. Substantial editing of AI output doesn't change its classification. The disclosure goes to Amazon, not readers. Check the current KDP Content Guidelines before publishing.

Can I copyright a book written with AI?

You can protect the human-authored parts. The US Copyright Office says AI-assisted works aren't barred from copyright, but outputs are protected only where a human determined sufficient expressive elements, and prompts alone don't count. This is general information, not legal advice, and rules vary by country.

Is Sudowrite or Novelcrafter better?

Sudowrite is easier and bundles a fiction-trained model; Novelcrafter is cheaper to start, stronger on planning, and lets you pick your own model, but needs an API key. Choose Sudowrite for convenience, Novelcrafter for control. Our Sudowrite vs Novelcrafter article compares them in detail.

Is there a free AI for writing a book?

Not a full one among these three. Sudowrite and Novelcrafter offer free trials but no permanent free plan, and ProWritingAid's free plan checks only 500 words at a time. Novelcrafter's Hobbyist plan can connect free local models, so the AI cost can be $0 while you still pay for the plan.