[hfhdndnfbdbd]

I think people in the comments are missing the point.

I might be wrong, but the point isn't comparing a modified The Great Gatsby to the original one. Of course that's not impressive and it's an easy thing to do.

The point of the exercise is supposed to be[1] that the model has the entire novel as context / prompt and so can identify (within that context), whether a paragraph is out of place. That is impressive and I wouldn't know how to find that programmatically (would you have a list of "modern" words to check? But maybe the out of place thing is hidden in the meaning and there's no out of place, modern word).

[1] I say supposed to be because the great Gatsby is in the training sample and so maybe there is a sense in which the model "contains" the original text and in some way is doing "just" a comparison. A better test would be try with a novel or document that the model hasn't seen...or at least something not as famous as the great Gatsby.