It is a thoroughly mediocre book. If I were truly reading it in a vacuum, I would have suspected that it was an early book by a now well-established middle-aged writer who had dredged it from a bottom drawer in the hope of quick cash.
The prose drove me to think of the dancing hippopotamus in Disney's "Fantasia". While it is often deft and occasionally lyrical, it is so self conscious that the whole is cumbersome and ponderous. I got the impression that Fitzgerald was constantly looking over his shoulder to make sure that the audience was properly cognizant of his cleverness.
The plot is standard stupid-people-being-unhappy stuff. There were apparently some grounds, at the time of publication, for reaction to the idea that people could be so monumentally vapid that their daily lives could kill people as collateral damage and then roll on with no shadow of consequence. What might have been outrageous in 1925, however, is boring in 2013-- and I suspect that even in 1925 the outrage would only have been feigned in the name of propriety.
With two exceptions, the characters are so thin that it is flattery to call them cardboard. The first exception is Gatsby himself, and he is a pulp hero, a creature every bit as improbable as Tarzan, Conan, or Doc Savage.
The second exception is the narrator, who is the closest thing to a real character in the novel. Unfortunately, he is badly marred by Fitzgerald's self indulgence. First person narrators have three faces: The character as he sees himself, the character as the author sees him, and the character as the prose itself reveals him to be. Ideally, the latter two are nearly identical, but not here. While Nick has great depth and passion relative to the other impossibly shallow characters, Nick is by his own admission, and his actions, fundamentally lacking in those things. And yet the prose, Fitzgerald's often deft, occasionally lyrical, and relentlessly self conscious prose, speaks of depth and passion that do not otherwise exist in the book.
I suppose I am required to mention the optometrist's billboard; it seems to be inescapable. I strongly suspect, given Fitzgerald's quirky and vaguely sadistic sense of humor, that it is what is known locally as a "black helicopter", that is, a prominent and absurd detail which exists solely to give critics a focus onto which they can hallucinate significance. I certainly hope this is the case, and think better of Fitzgerald for it.
I am told that literary academia regards this piece of mediocre fluff as one the best books ever written. Since I am predisposed to believe that literary academia is intellectually (and by extension, morally) bankrupt, this fact serves to confirm my opinion.