What was the author's purpose in writing The Great Gatsby?
This novel can be seen as an exploration of class aspirations in America, of a materialistic distortion of the American Dream of self-determination and self-improvement, and a satire on contemporary values in the Jazz Age.
Beyond it's value as a work of art (which may be its principal value as the work is a considerable achievement of form, craft, character, and language), Fitzgerald's novel is open to claims that it is intended to affect the reader's thoughts in any of these thematic areas.
The novel is written in the form of a satire. This gives credence to the notion that the book is meant to highlight the moral failings of a society mesmerized by the trappings of wealth, by the bright lights of glamour, and the false beauty of accumulating material goods instead of living a "good life".
These comments are all drawn from the novel's depiction of the upper class in America during the Jazz Age.
The Great Gatsby is the tale of the irresponsible rich. Originally, the title of the book was “Trimalchio,” based on an ancient satire of a man called Trimalchio who dresses up to be rich.
Going back to the question at hand, we might say that Fitzgerald wrote the novel to suggest that the aspiration to become wealthy in America was, in reality, not as great as people imagined it to be. In this way, it is a novel of disillusionment.
Yet, there is a great hope at the center of the novel. Though Gatsby, like Trimalchio, is only dressed up to be rich and is therefore essentially false in his self-presentation, there remains something true about his character.
[Gatsby had] an extraordinary gift for hope, a romantic readiness such as I have never found in any other person and which it is not likely I shall ever find again.
Keeping Nick in mind (as a man who learns to look past the surfaces of people), we can say this is a novel intending to find the heart of virtue in an age where it has become obscured; lost in the bright lights and the nihilism of shallow ambitions.