1. Gatsby's books
An owl-eyed man at a Gatsby party sits in awe in the library, murmuring with amazement that all the books on Gatsby's shelves are "real books":
"See!" he cried triumphantly. "It's a bona-fide piece of printed matter. It fooled me. This fella's a regular Belasco. It's a triumph. What thoroughness! What realism! Knew when to stop, too - didn't cut the pages. But what do you want? What do you expect?"
Books used to come with their pages uncut, meaning that the sheets that are folded to make the books aren't sliced open on the top. You'd have to cut them open before reading. If you didn't, everyone would know that you hadn't actually read the book.
Gatsby's uncut books tell us that much of what Gatsby presents to the world is a facade. He wants people to believe that he's a well-educated man, an Oxford man, but in fact he only spent a short time there after the war. He wants people to think that he's well-read, but he's never even cracked the covers. So, the simple answer is that the books represent the fact that Gatsby is a fraud. He's built up an image of himself that isn't consistent with the facts of his life. But you could also argue that the unopened, unread books represent Gatsby himself: eternally mysterious, eternally unopened.
2. An owl-eyed man
Owls are a symbol of wisdom, but can also be an omen of death. Did you notice that it was the owl-eyed man who had the car accident outside of Gatsby's house? And that, shortly after he got out of the car, he revealed that someone else was driving? He really is acting as an omen, or a harbinger, of death.
But it's really the glasses bit that has our hearts beating faster. A man with large eyes and spectacles would be expected to be more perceptive than those around him. And Fitzgerald makes sure we notice the glasses; the guy is always taking them off and wiping them: "He took off his glasses and wiped them again, outside and in". Is all that wiping the reason that the owl-eyed man is the only one of Gatsby's guests who really gets him?
Well, he is the only guest who, in doubting Gatsby, is also wise enough to investigate further. And when he does investigate, he understands what he sees: "See!" he cried triumphantly. "It's a bona-fide piece of printed matter. It fooled me. This fella's a regular Belasco. It's a triumph. What thoroughness! What realism! Knew when to stop, too – didn't cut the pages. But what do you want? What do you expect?".
There's a lot stuffed into that paragraph, so let's unpack it: first, the owl-eyed man is surprised (and a little delighted) to find out that the books are real. So, Gatsby's done his due diligence in trying to fool people: he's actually gone out and purchased real books. But, as the man discovers, he hasn't cut the pages and actually read them. Gatsby knows how much he has to do to fool people, and he knows that he doesn't need to cut the pages. Nobody in this crowd is going to check, because they're just as fake as he is. That's what the owl-eyed man sees.
3. The eyes of T.J.Eckleburg
The first time we see the eyes of T.J. Eckleburg, they're looming over the valley of ashes, which Nick and the others have to pass through any time they travel between the Eggs and the city: "above the grey land and the spasms of bleak dust which drift endlessly over it, you perceive, after a moment, the eyes of Doctor T. J. Eckleburg". The ashes are, as ashes tend to be, "desolate" and "grotesque". Think of the valley of ashes as one big, grey reality check. Compare Gatsby's lavish parties of fresh fruit and live music and champagne to this land of smokestacks and ash-men, and you quickly realize that not all the world is as privileged as our cast of characters.
But the valley of ashes can also be seen as more commentary on the American Dream. The America of The Great Gatsby is ashen, decaying, and barren. And the Wilsons live there, which means their whole sordid story—the infidelity, immorality, lack of compassion, and anger—is associated with this failed American Dream, too.
Which brings us to the eyes. T.J. Eckleburg's billboard is the second notable pair of eyes in the novel (owl-eyes being the first). But these ones are a little different from those of the party-going bibliophile: "The eyes of Doctor T. J. Eckleburg are blue and gigantic—their retinas are one yard high. They look out of no face, but, instead, from a pair of enormous yellow spectacles which pass over a nonexistent nose".
This description is only slightly less freaky once you realize that they're not actually giant disembodied eyes; they're on a billboard, an ad for an eye doctor.
Nick goes on for three sentences about these weird, disembodied eyes before actually explaining that they're on a billboard. He gives your mind time to picture eerie images, to wonder what's going on, even to form other notions of what the eyes could be. Clearly, to us, the readers, the eyes are more than just a billboard.
Not long before the Tom vs. Gatsby showdown, Nick notes the eyes again keeping a "watchful vigil"; and then, George takes Myrtle to the window (from which, we know, the billboard is visible) and tells her she can't fool God. Wilson makes the same connection you might be: the eyes of T.J. Eckleburg are always watching, and so are the eyes of God.
There are a few directions you can take from here. The first is that, despite the absence of religion from the characters in this story, God is still there. He's all seeing, ever-present, and, as Nick points out, frowning. Things are not well in the valley of American ashes. The other shot you could take at this is to say that God has been replaced by capitalism. Instead of a truly religious representation, the best this world can do is manifest God in a billboard – an advertisement.
4. The green light
We hate to think about the amount of ink that's been spilled writing about the green light in Gatsby: the "single green light" on Daisy's dock that Gatsby gazes wistfully at from his own house across the water represents the "unattainable dream," the "dream [that] must have seemed so close that he could hardly fail to grasp it".
But the green light also represents the hazy future, the future that is forever elusive, as Nick claims in the last page of the novel: "Gatsby believed in the green light, the orgastic future that year by year recedes before us. It eluded us then, but that's no matter – to-morrow we will run farther, stretch out our arms farther….". But if the green light represents Gatsby's dream of Daisy, in the past, then how does it represent the future, as well? Is the future always tied to our dreams of the past?
One last thing. Red-green traffic lights began to be installed in the U.S. in the 1910s and 1920s. Coincidence? Maybe.
