Fitzgerald bandied around several titles (Under the Red, White, and Blue) before his editor/publisher encouraged him to go with The Great Gatsby. So, he obviously wanted to write not only a great American novel, but a critique on America's moral wasteland. He's writing about two Americas.
According to Cornell Professor Don McCall (who cites another Cornell professor below):
The title of the novel has a special ironic distinction: it says two things at once. First, Gatsby is truly “great,” a legitimate hero. Second, he is a figure in a sideshow, a freak, a carnival oddity, “The Great Gatsby.” At one point the book’s narrator, Nick Carraway , sees Gatsby as “a turbaned ‘character’ leaking sawdust at every pore.” And the more we get to know the man, the more clearly the two meanings of the title are right—he is indeed exemplary, and he’s a grease-paint Wonder of the Western World striding majestically around on a platform. Cornell Professor Arthur Mizener, the first and...
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