The Picture of Dorian Gray by Oscar Wilde
Pretty much everything Oscar Wilde wrote would please a Fitzgerald fan, but we think The Picture of Dorian Gray has just the right undercurrent of darkness to fit the bill. The only novel Wilde ever published, it tells the disturbing story of the narcissist Dorian Gray, who sells his soul to ensure that a portrait of himself will age rather than his own face and body. Having ensured his eternal youth, he basically acts like he's 1960s Keith Richards, partying it up while his portrait starts looking like... 21st Century Keith Richards. Wilde, as always, is so hilarious and clever about his moralizing that you barely notice how heavily he lays it on.