Prose that sounds like a book
One model for everything
- Flat prose in the chapters that matter most
- Mature scenes refused halfway
- Waiting months for a new model to reach your tool
The model that fits the scene
- Claude for the strongest prose
- Grok for mature and explicit themes
- New top models on Ultra first
Three models, three strengths
Gemini · 15 credits / chapter
Good overall quality, follows instructions well.
Grok · 20 credits / chapter
Creative, strong at mature and explicit themes.
Claude · 30 credits / chapter
Best prose quality.
How you choose
01Step
Pick a model
Choose Gemini, Grok or Claude when you write or regenerate a chapter. The credit cost is shown next to each.
02Step
Open All other models
Ultra opens every model on OpenRouter for chapter writing.
03Step
Connect your key once
Paste an OpenRouter key in settings. Actions that run on it cost 1 credit.
What it writes
Chapter one of The Harbor Light, a demo book on AIWriteBook.
Chapter 1 · The Storm Warning
Nell Byrne had kept the harbor light on Gull Point for eleven winters, and she had never once let it go dark. On the first evening of November the radio crackled with a storm warning, and she climbed the iron stairs with a can of oil and a flask of tea. Below her the fishing boats were tying up two deep along the quay. Her brother Tom was out past the reef in the Mary Ellen, and he had not answered his radio since noon.
What Ultra adds
Newest models first
When a better model ships, Ultra gets it before other plans.
100+ models
Any OpenRouter model for chapter writing, searched by name.
1 credit actions
Actions that run on your own key cost 1 credit.
Per chapter control
Mix models inside one book.
Model choice is in every plan. The newest models and OpenRouter access come with Ultra.
See plansQuestions
Gemini, Grok and Claude are built in for fiction. Non-fiction uses Gemini and Claude. With an OpenRouter key you can write chapters with any of the 100+ models on OpenRouter.
Ultra gets new top models first, plus your own OpenRouter key for 100+ models at 1 credit per action that runs on your key.
Yes. Choose the model each time you write or regenerate a chapter.
Claude. Grok is strongest for mature and explicit themes. Gemini is the most economical.
Only for the extra models. The built-in models need nothing but your credits.
Write with the best model available.
Start free, upgrade to Ultra when you want every model.