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.

Maya Angelou reads from "The Heart of a Woman"