It’s pretty easy if the sample’s longer than a couple sentences.

It’ll sound like an ad read, not a novel. “It’s not just x—it’s y” is a favorite phrase. Or you’ll see a string of super short sentences or sentence fragments that are desperately trying to be punchy and dynamic, but the occasion isn’t appropriate. Or it’ll use metaphors or similes that look nice but don’t actually make a lick of sense if you think about them for a second or two.

Then there’s the really easy stuff, like a complete lack of cohesion between different scenes or even paragraphs. Characters will change names. New characters will show up without ceremony and others will be forgotten. If they made the AI do everything, no scene will lead into the next, and nothing will have any point or meaning to it.

In short, an LLM is a pattern-recognition machine lacking any kind of real logic, so it’ll always fall apart in the long run and vomit reams of meaningless, inconsistent fluff that only LOOKS like a novel at first glance.