Here's the question Michael Cunningham needed to ask of his protagonist, Peter Harris, before starting this novel: if you had to do it all over again, would you still fall in love with yourself?
Peter, a study in self-absorption to the point of solipsism, is obsessed with himself and his malaise but in an intensely undramatic, uninteresting way. Part of this is conceptual. If you're going to write about the howling cliche of a middle-aged man going through a mid-life crisis, he had better be deeply entertaining, wildly fascinating, or at least humorously self-aware - Harris isn't and Cunningham can't seem to conceive of him as anyone other than a real Sad Sack burrowing boringly to the center of his underfurnished soul for 238 pages.
Counterexamples make the point best. Read Roth's "Portnoy's Complaint" to see how it's done: self-obsession, self-seriousness, self-mockery, and of course, as my old nuns would say, self-abuse, all turned inside out in a rocketing id-on-the-loose carnival of laughter, lethality, and the annihilation of convention. Note to self: it works because it's funny.
A more recent example is Russo's "Straight Man". Like Portnoy and Harris, Russo's man, Devereaux, is the walking cliche of the middle-aged man in crisis but he has the wit not to take himself or his situation at all seriously, thereby lending them both a subtle gravity. The result is a comic masterpiece which moves with narrative speed, episodic fleet-footedness, and offhand elegance. Unexpected bonus: beneath the laughter there runs a wry river of actual wisdom about life, relationships, regret, and loss. Of human beings, their discontents and what strategies we should use against the dark, Russo has cut more than Cunningham has printed.
What Cunningham fatally misses is that Peter's sad view of his sad, unhappy I-feel-so-sorry-for-myself life is essentially (of course I mean absolutely) comic. That's the only way to view it artistically and have a hope of bringing it off plausibly for the reader. I mean, who really wants to read the aching lament of an overprivileged beauty broker nattering on about his lost youth, dead brother, aging wife, pretty brother-in-law, and how beauty fades? Doesn't that sound like the setup to a joke?
We are in Peter's head throughout and it's a mighty boring place. While we're waiting for characters to respond in dialogue Peter's given to endless stone-faced commentaries on behavior, or society, or art, or something. Some of this is anthropologically interesting, especially some of the art stuff, but even there it's interesting in an essaylike way, not a novelistic way. Mostly these observations sound like homework Cunningham's doing for a Phd thesis. He's trying very hard to sound smart and observant but it comes across in laborious, portentous, sententious ways (just the kinds of words he overuses), and worse, the story stops dead in its tracks every time. Connected to this is Cunningham's maddeningly obtuse inside-the-sentences technique of qualifying (almost) (every) statement with switchbacks and counters and doubts and second thoughts - the staccato stopping and starting may strike Cunningham as the mental portrait of a smart guy being smart but it reads like the transcript of a dull guy being repetitive (repeatedly).
Part of Cunningham sweating too much to convince of how VERY SERIOUSLY we should take Peter's dilemma is the assiduous way he lards the text with many literary/artistic references as if trying to take on mythopoeic freight by association (Mann's "The Magic Mountain", Fitzgerald's "Great Gatsby", and any number of artists, old, modern, and obscure). The effect is weightless grandiosity. In fact, straining for SIGNIFICANCE this way makes the shallowness of Peter's pedestrian display of consciousness all the more obvious.
Instead of reading this heavy-handed novel, try the recently published "An Object of Beauty" by Steve Martin. I haven't read it yet but it is also about the New York art world and has the great advantage of being written by a man who started out as a comedian.
Or read any play by Moliere. He'd have known what to do with Peter Harris: "The Imaginary Crisis and How I Overcame It".
Final advice: Laugh. Repeat. It's our only defense against seriously sad novels like this and the onslaught of what awaits.