I have tried to organise my critique of this book for brevity, as I don't really have an 'essay' per se to write, but merely... a bunch of criticisms.

Anti intellectualism

There is a weird strain of anti-intellectualism in this book about a Professor of Literature (adjunct professor whatever) who is married to a Professor of Philosophy.

Could not... hold her face in a steady expression of interest while her colleague talked at length about the surprising importance of cheese in medieval theology.

... But why not? I understand listening to a boring person, but this was a poorly chosen 'boring fact'. But in fact the entirety of the book has this constant suppression of genuine intellectualism. What I mean by that is that Phoebe has been around intellectuals her entire adult life and was presumably nerdy before that. And yet she is reduced to being an arbiter of 'Sex on the beaches' or 'Sexes on the beach'. She uses a highly facetious argument about the etymology of the word balcony to argue that she is not 'in her room' and is met with a 'Who are you?'? This argument is not a real argument, its basically just attempting to confuse the listener through 'too much information at once'.

The people around her are impressed by her professorship but no one asks her about it in depth, not even Gary. Her professorship is a prop in the book, and there are so many times that she says something a little nerdy and people basically go 'why are we talking about this?'

What the hell are you guys talking about?

Real smooth one Jim.

Her husband, Matt, is also guilty of this, he doesn't once make a genuine point or seem to have a real thought from the perspective of someone who spends all day and night reading and thinking about philosophy. You don't get to be a real professor by just KNOWING things, that is actually the lowest order of knowledge. A professor has done original research, has opinions on their field wide and far. It isn't something you can just do casually whilst being otherwise completely unaffected by it.

Phoebe feels the sudden urge to argue. She has a contrarian imulse that stirred within her during class or at a party when anybody had the audacity to talk in absolutes. She never acted on it, though, because she never wanted to be accused of talking in absolutes. Those people were her least favourite.
But what does she care now? Might as well go out showing the world what she got from all those years of studying.
"The word balcony is borrowed from the Italian balcone," Phoebe says. "Derived from medieval Italian balco, which originally meant 'scaffold'. And that comes from a Proto-Germanic word balko, which probably meant something like 'beam.'"
The bride stands there, confused.
"So, taken all together, we know that the word balcony originally referred to the beam or structure that holds up the balcony." Phoebe releases a long, slow exhale of smoke before her final conclusion. "That's how far outside the room it is. The balcony is not even the balcony."
"Who are you?" the bride asks.

Look I would enjoy that if it wasn't meant to be a scene where someone finally takes agency over their life. How is this taking agency? Putting a really quite crappy argument out into the world (so if a menacing man was to climb onto the balcony, could you get him removed because he's in your room or would you respect the balcony's judicial distiction?) that falls flat because she's presenting it to an idiot.

Maybe the point is that she's meant to feel empowered because she's finally just saying what's on her mind and doesn't care how its received, right on, but even so its still just a limp fish of an argument and the author had all day to come up with a better one and that's the one they went with? And to finish it off with 'who are you?'?

Who are you is such a genuine cliche...

but then... it eclipses it with the sentences right after:

The bride sounds genuinely improssed, and Phoebe will admit that she has not lost the capacity to enjoy this kind of moment. Knowledge is power, all her teachers told her as a kid, which is why she spent the best part of her youth in quiet corners of the libraries, reading books as quickly as she could. She wanted to be stronger, bigger. She know that she would never be taller than her father, never be bigger or stronger, and that this was the only way to one day see beyond her father's house.

The self-congratulatory background exposition is really... something considering the rubbishness of the argument and it just... attacks my sense of respect for the character. I already believed she was cool because she studied literature, all this ego posing to an idiot who clearly is not her intellectual equal (ahuh? like she's some sort of intellectual titan with arguments like that?) and then feeling really good for... 'winning' an argument that essentially just defined words according to their 2500 year old root word (Proto-German apparently is dated to around 500BC) and letting the fact that the bride apparently has no real faculties except to be cudgeled under the Phoebe's need for self-actualisation really doesn't make me think well of Pheebs.

Shallow moral aphorisms

I think we talk about happiness all wrong. As if it's this fixed state we're going to reach. Like we'll just be able to live there, forever. For me, it comes and goes. It shows up and then disappears like a bubble.

I think that this book deeply wants to be philosophical fiction - but it literally does it worse than any philosophical fiction I've ever read. Its just so shallow and obvious and preachy. Like the interlocutors are speaking directly to the audience, self-help style.

Performing humour without being funny

They stare at Elizabeth's bed.
"Is this were you'd sleep?" he asks.
"I think this is where Elizabeth's ghost sleeps."
He laughs

"What's actually in this drink?" Phoebe asks. She sits back against the side of the boat and the wind picks up her hair. "It's so good."
"A vacation," Gary says.
"Right," Phoebe says. "But what kind of vacation? Like a beachfront condo in St. Thomas?"
Gary takes another sip as if he's a sommelier."I'm getting more, RV visiting Civil War battlefields in the South for three days."
Phoebe takes another sip. "Really? I don't taste any battlefields."
"No?" Gary says. "You clearly don't have a complex palate. Or a father who once dragged you to all the Civil War battlefields as a child."
She laughs. He laughs. Jim just watches them talk as if the conversation is too weird to join.

Honestly Jim is doing solid as a wing-man to be honest in that situation. Just be quiet and let them have their moments.

But I did think that the book tried really really hard to show that when two people get along, they're funny. Banter was the primary yardstick of compatibility. And that's fine, fair enough, but it did at a certain point, to me, stop being show, and started being tell. Mostly because the jokes just weren't funny. As such, you had to suspend your disbelief that the humour was really working, and then be cudgeled round the head repeatedly that NO REALLY WE'RE FUNNY TOGETHER NO REALLY. Like does 'show' become 'tell' when the same thing is basically repeated constantly?

As well, at some point, people don't just continue constantly bantering. They talk about stuff. Where was the question about Civil War battlefields? Or anyone actually asking Phoebe the entire book about... literature in any sort of in-depth way?

The ending

Matt comes back. And he comes back with nothing to say about it. As in, specifically, what he says is so non-specific, and Phoebe so effete in her interrogation of him, that its positively annoying:

"Most days, I wake up in Mia's house and I think, Where the fuck am I? I am here, with someone else's child, making pancakes on someone else's stove. A fucking electric stocve that basically takes an hour to heat up. Mia and I, it's not right. I don't know what I was thinking.

That doesn't really do a good job explaining why he fell out of love with Mia actually... Like was his point that he didn't actually like her and was just because of Phoebe's depression which made it easy for him to do that? Like for 2 years he lives with someone and he once again abandons them LIKE THAT in ONE DAY?

Like I get cheating, I get wanting to make amends and feeling extremely guilty and wanting to go back to your ex. I just think that there's little in the way of genuine learning expressed on his part, and he could have articulated a far richer interiority if the author had wanted him to.