OpenAI's GPT-4 language model is already world-famous. We've adjusted all the details of how the app writes chapters to take full advantage of its power. You can turn it on and off for each of your stories as you wish, in story settings.
You'll notice that GPT-4 is much better at keeping track of complicated details in long, multi-chapter stories over time. You should see fewer silly mistakes (like a character getting their wallet stolen, then taking out their wallet to buy something in the next chapter). It's overall much better at stories with lots of moving parts, like mysteries.
GPT-4 is still in early preview, and can sometimes have errors. It can take a lot longer to write chapters, and writing style is not noticably improved. In some cases, the writing seems less vivid and fiction-appropriate. This will probably get better in the future. If your story is not complicated, or it's not important that the plot threads and details are perfectly consistent, then GPT-4 probably isn't worth it.
GPT-4 is still in its early preview stages, and is much more expensive than the regular GPT-3.5 that we normally use. It should get cheaper as time goes on, but for now, we have to charge 30 coins per chapter instead of the usual 1 coin.
While you are free to turn it on and off, you'll get the most benefit from GPT-4 if you turn it on at the start of a longer story and leave it on. You won't see as much improvement if you just turn it on for a single chapter in the middle of an existing story.
Try out GPT-4 to see the future of AI writing. Right now, it's too expensive for most people to use all the time. You'll see the most benefit in complicated, longer stories, and when you really care about the details.