If intelligence were sufficient to make for a good novel, then Isabel Fonseca would certainly have succeeded in producing one. “Attachment” (Knopf, 320 pages, $23.95), the fiction debut from the wife of writer Martin Amis, is not only smart but smart in a pleasing and all-too-uncommon way: It’s insightful about grown-ups in the throes of grown-up emotions. That’s the good news.

The novel begins with Jean Hubbard, a freelance columnist, and her advertising exec husband Mark living happily on a remote tropical island, taking a break of indeterminate length from life in London; the respite is ruined for Jean when she intercepts a sexually explicit letter addressed to Mark, which she chooses not to confront him about. Months later, Jean receives abnormal mammogram results that prompt her and Mark to return home, where their daughter attends college and takes care of the family house. She soon learns that her father will undergo serious surgery in New York, where she grew up, so she hops on another plane and, back in America, winds up growing close to an old flame.

Despite the territory — and the intrigue — covered, “Attachment” doesn’t generate much narrative tension. Instead, it plods along episodically, leavened by moments of introspection from Jean, whose reaction to her husband’s infidelity is far richer and more nuanced than that of fiction’s garden-variety scorned woman, and whose ruminations offer much of the value of the book. Affairs, Jean thinks, forced the aggrieved party “to unpick and unravel themselves year by year until they got back to where they started in the marriage, and then begin again as they found themselves now, all squiggled and jangly and unsure.” That prompts a troubling thought: “Jean now saw what was expected of her: she’d not only have to endure Mark’s affair but be improved by it” — that is, treat it as a wake-up call to revamp her appearance and career.

But Jean is also capable of thinking philosophically, wondering whether her reaction is selfish in its focus on the affront to her pride; doesn’t love entail a more generous spirit, with some kind of allowance for the beloved’s weaknesses? Jean imagines how she’d react if not her husband but her daughter Victoria had wronged her. “Wouldn’t she go on loving Victoria if she forged her mother’s checks or ran a brothel out of their house on Albert Street, or secretly converted to Hinduism and married her boyfriend in Mumbai?”

Ms. Fonseca is commendably clearheaded and unsentimental about the nature of attachment, particularly in long-standing relationships. In a moment of pique, Jean muses that her husband is an “ass.” She “hated the way he pushed when he wanted someone to drink with; hated even more his already being high without needing her high alongside him,” Ms. Fonseca writes. “He was a bully when he was drinking, a bully cloaked in amiability, a bully and a bore.” This is precise and real, and it captures how a thoughtful person might very well feel at moments, even about someone he or she loves. Ms. Fonseca knows how in the process of being close to other people, we necessarily stockpile voluminous material with which we occasionally indict them, whether silently or aloud.

The problem for “Attachment,” however, is that it’s not at all clear what Jean is like when she’s not methodically analyzing her marriage. And she’s the most fully realized character of the bunch! It takes artistry to create vibrant characters — characters who have even a fraction of the presence of a real-life human being — and artistry is precisely what “Attachment” lacks.

Consider this scene between Jean and her 20-year-old daughter, Victoria. Jean is “padding around in a pair of loose yoga pants”:

“Hey Mum, you look really good in those.”

“These flattering pantaloons?” Jean held them oaut at their greatest, clownish width. “What do you think? Ideal pants for a pantisocracy, everybody gets a pair.”

From there, Jean and Victoria train their rapier wits on another aspect of Jean’s apparel: a pair of oversized Garfield the cat slippers. (“Sort of panthery,” Jean says, “you know, for evening.”) It’s not that this kind of banter is too hokey to be believable; on the contrary, its undeniable verisimilitude to humdrum domestic life is its only recommendation.

At times, it’s unclear if Ms. Fonseca is writing a serious novel or chick lit. Consider this bit when Jean’s sister smokes a cigarette in her presence: “[F]or once she wasn’t hiding it from Jean in a bid to seem more perfect,” Ms. Fonseca writes. “Her sister had lost weight and not all of it in her head.”

There is much that is aesthetically confused about “Attachment,” which is why the book doesn’t hang together, either on the level of the sentence or in terms of the overall shape of the narrative. Intelligence may be a necessary precondition but literature is to a large extent a product of style. When that is absent, you end up with something no more appealing than a meretricious letter to a spouse.

Ms. Waldman’s writing has appeared in the New York Times Book Review, the New York Observer, and Time Out New York.