I Let ChatGPT Edit My Book. Then I Let Grammarly. The Difference Was Embarrassing.

I gave ChatGPT a chapter and said 'tighten it.' It came back smoother and completely unlike me, with three jokes I'd never make and a metaphor about a lighthouse. Grammarly, given the same chapter, moved commas, flagged two '%' where I meant 'percent,' and left the jokes alone. One edited, one corrected.

For a book, voice is the product. ChatGPT's tidy version read like a competent ghostwriter took over, which is exactly what I didn't want. Grammarly's version read like me after coffee. The embarrassment was realizing how many 'very' and 'really' I'd leaned on; Grammarly's count shamed me into cutting them by hand.

ChatGPT earns its keep earlier, in the messy draft, when I'm stuck on a transition and it offers three. Then I write the transition myself. Grammarly earns its keep at the end, on the prose I've already claimed. Using ChatGPT at the end is how my book nearly stopped sounding like mine.

The one place they overlap is clarity, and there Grammarly is safer because it shows the rule. ChatGPT 'improves' a sentence and I can't always say why, which is dangerous in nonfiction where a wrong rewording changes the claim. Grammarly's suggestions I can accept or reject with eyes open.

Verdict: ChatGPT for getting unstuck, Grammarly for getting clean. Letting either do the other's job on a manuscript is how you ship something that's polished and wrong, or correct and not yours.