Nick Hornby has won renown for his hilarious and painfully accurate portraits of certain types of contemporary men in books such as “High Fidelity,” “Fever Pitch” and “About a Boy.” His new novel, “How to Be Good,” is narrated by a woman, Katie Carr, but she’s (unhappily) married to a perfect candidate for the Hornby treatment: David, whom she describes as “the definition of aggrieved. Permanently.” Katie works as a doctor in a North London clinic, providing most of the financial support for David and their two children, Tom and Molly, while David writes a column called “The Angriest Man in Holloway” (that’s the liberal-minded neighborhood where the family lives) and labors over a mean-spirited satirical novel about a “touchy-feely” company that “sells banana elbow cream and Brie foot lotion and lots of other amusingly useless cosmetics.”

David devotes his journalistic energies to denouncing such modern-day annoyances as grievance counselors, old people who don’t have their fare ready when they board a bus, “women who wear headscarves,” homeopaths and restaurant critics. Katie half wishes he’d undergo a “violent political conversion” and become a conservative ranting about “poofs and communists” because “it must be very unsatisfying to have such tiny outlets for his enormous torrent of rage.” Here’s how she describes to David a typical evening with their friends Andrew and Cam:

We walk in, and then Andrew says that so-and-so’s a wanker and his new book is awful, and you say that the new film by somebody else is unintentionally hilarious — even though nine times out of ten I know for a fact that you haven’t seen it — and Cam and I sit there smiling and sometimes laughing if you’re being funny instead of just plain nasty, and then you get drunk and tell Andrew he’s a genius, and he gets drunk and tells you you’re a genius, and then we go home.

The specimen that Hornby has under consideration here, then, is the quintessential Angry Guy, albeit what seems to be a peculiarly British variation on the breed. In America, the Angry Guy is every bit as resentful as David but much less cautious. Instead of fulminating about headscarves, the American Angry Guy does things like send e-mails with what he imagines to be devastating ripostes to, say, any female writing for an online magazine who dares to suggest that a woman’s lot might consist of something more than pregnancy and bare feet. Whatever the wording of those e-mails, they all communicate the same information, which is: “I got the worst of a nasty divorce from a woman who now makes more money than I do and has since married a man who’s got better things to do than sit in a grubby recliner all day watching Fox News and thinking up taunting messages to e-mail to total strangers.”

David does, in fact, undergo a conversion in the course of “How to Be Good,” and it’s a transformation that prompts him to tell Katie, “I’m a liberal’s worst nightmare.” But that’s not because he suffers from the conservative American Angry Guy’s delusions of rhetorical grandeur. It’s because he truly has become a liberal’s — specifically Katie’s — worst nightmare, something far scarier than a crank who’s picked up a couple of taunts from Bill O’Reilly. David is no longer an Angry Guy; now he’s practically a saint. “I think everything that you think,” he explains to his wife. “But I’m going to walk it like I talk it.”

David’s change of heart starts out as a bit of marital warfare, a bitter sport at which both partners are “highly skilled” according to Katie. Plagued by a bad back, he visits a healer named GoodNews, primarily because he knows it will mightily annoy his physician wife to learn that he’s paid 200 pounds to a semi-indigent former DJ who cures people simply by touching them. However, the healing works, and spectacularly well. GoodNews even cures Molly of her chronic eczema, and when David learns that Katie is not only miserable enough to be considering divorce but has also been having an affair, he goes back to GoodNews for an overhaul of his psyche.

Suddenly Katie, who only a few days earlier declared, “I don’t want David to be David anymore,” has a whole new husband. Instead of snarling and griping, he asks the kids about their schoolwork, manages to enjoy a night at the theater without sneering and tells Katie that he wants to reintroduce “communication” and “intensity” to their sex life. (She’s not pleased, feeling that their old “button-pushing routine” at least “had the virtue of efficiency.”) He also gives all the money in her wallet to a homeless man, donates Tom’s computer to a battered women’s shelter, invites GoodNews to move in and, with his new spiritual mentor, launches a campaign to persuade everyone in the neighborhood to shelter homeless youths in their spare bedrooms.

From this point on in “How to Be Good,” Hornby could have opted for a simple farce: Suffering the consequences of getting what she wished for, Katie finds herself saddled with an impractical, sanctimonious do-gooder spouse. Roped into playing the naysaying role David has abandoned, she can only look on as the well-meaning but daft projects of David and GoodNews end in debacles while she waits for her husband to come back to his senses.

Hornby doesn’t take the easy route though, which is something that distinguishes his deceptively light fiction from the usual contemporary comedy of manners. It turns out that David’s schemes don’t all blow up in his face. Yes, one of the homeless kids rips off his hosts, as Katie predicted, and another gets restless after a couple of weeks and disappears. But a handful of them fuse into unconventional but happy families with the people who take them in. Tom and Molly get mad when David gives away their stuff, but they get over it. Katie is left to sputter about how her husband’s newfound charity will never work, when the truth is that it does, if imperfectly so.

For Katie, who has always considered herself a “good person” (“One of the reasons I wanted to become a doctor was that I thought it would be a good — as in Good, rather than exciting or well-paid or glamorous — thing to do,” she says), this amounts to a moral revolution. She’s forced to scrutinize her own generosity, her patience, even her love for her children, and to her dismay she comes up lacking over and over again. “How to Be Good” is partly a wry marital comedy about how a spouse’s change of heart invariably destabilizes his longtime partner’s own identity, but it’s also a thorny parable about the dangers of complacent, conventional self-satisfaction. It’s also a very funny and shrewd novel, like Hornby’s others, full of acerbic observations about book-buying habits, the virtues of friends who don’t really listen to what you say, the tactlessness of children, movies that all seem to “involve spacecraft or insects or noise” and the poisonous bitchiness of those dissatisfied souls who hover in the margins of the creative life. But unlike Hornby’s previous protagonists, lost boys who need only master the relatively simple task of making a commitment, Katie faces a predicament that doesn’t lend itself to commonplace solutions. The truth is, few of us really are “good people” if we’re even a tiny bit rigorous about defining that term. Sometimes the most that we, like Katie, can hope for is to be just about good enough.