The green light. I am undone.

So we beat on, boats against the current, borne back ceaselessly into the past.

I have known that line since school without ever once having earned it. This summer I finally earned it, in a static caravan outside Whitby, in the rain, with a cup of tea going cold on the windowsill and my wife doing a jigsaw of a lighthouse.

Here is the thing nobody warned me about: it is short. Not a word wasted anywhere. Every paragraph has been polished until you can see your own face in it, and the prose has that quality of a thing lit from the inside, like a paper lantern, or a wound that has healed over something still bright. Fitzgerald is doing four jobs at once on every page — plot, weather, symbol, and that terrible tender ache underneath — and you never once catch him sweating.

Nick Carraway is literally the beating heart of this novel. Everybody talks about Gatsby, and fair enough, the man throws a good party. But the book belongs to the watcher on the lawn, the one who reserves judgement and then cannot help himself, the one who calls across the grass at the end that Gatsby was worth the whole rotten lot of them put together. That is Loyalty. That is a man finally choosing a side. I found it enormously moving and I am not embarrassed to say that I welled up next to a jigsaw.

The shirts. Oh, the shirts. I have read that scene four or five times now and I still cannot properly explain why a man throwing shirts onto a bed and a woman crying into them is the saddest thing in modern literature, but it is, and if you can get through it without something going tight in your chest then I would gently suggest a check-up.

And then there is the Valley of Ashes, which is where the book stops being a romance and shows its teeth. Those enormous blind eyes up on the hoarding, watching over the ash heaps and the small grey men working away at them. Doctor Eckleburg is God with the paint coming off, and Wilson standing underneath him in his grief is one of the great images of the century; you cannot unsee it once it has been shown to you.

Where I lose the last mark, and I have gone back and forth on this all August, is Daisy. She is a voice full of money and a white dress and one catastrophic decision, and I never quite believed in her as a woman rather than as a weather system. Perhaps that is deliberate. Perhaps she is meant to be a screen for a man to project five years of longing onto, in which case the fault is mine for wanting more of her. But I did want more of her.

Tom is superbly horrible. Jordan is far more interesting than the plot has room for. The party chapters are the best party chapters ever written, and I do not even enjoy parties.

What I didn't expect, and what has stayed with me longest, is how much of it is about class in a way I recognise from here, from England, from my own street. Gatsby buys the house, learns the accent, gets the shirts right, and none of it matters, because Tom Buchanan can smell where he came from through a wall. That never goes away. My father spent his entire working life on the wrong side of a wall like that and it is not a thing you get over.

A word on the edition. Mine had the cover with the eyes and the mouth on the dark blue and it sat on the caravan table looking better than anything else in there. Two pounds fifty in a shop in Scarborough. Best two pounds fifty of my year.

One small confession. I had it in my head, for about twenty-five years, that Gatsby is shot by Tom. He is not. I said this out loud in the caravan with total confidence and my wife looked up from the lighthouse and said "no he isn't," and she was right, and she has not let it go since.

Nine out of ten. Read it in one sitting if you can, preferably somewhere with weather.