A gag is comedy's sucker punch. A well timed one can be devastating.

But writers who rely on them run a risk. A gag anticipated, after all, becomes kitsch -- like badly choreographed martial arts, or slapstick comedy.

So it's a minor miracle that Ian Frazier can repeat the same gag throughout "The Cursing Mommy's Book of Days" and not only get laughs each time, but a deepening sense of social critique, as well.

Very little of this novel can be quoted here. Basically, it depicts in diary form a year in the life of a stay-at-home suburban mother of two. She wakes at dawn as her husband slinks out the door to his crushing law-firm job. She rouses her pharmaceutically dependent children, and sets about her day.

But that's just the beginning of her work. Their house is collapsing, her husband is unraveling, the kids' medication isn't working and, to top it off, the evil HMO that provides their care is beginning to squeeze the family on premiums.

It's enough to make one snap, which over the course of this short book Cursing Mommy does. On every page, she slips hilariously from the gentle register of a woman just barely keeping it together to one whose swearing ability would make even George Carlin blush. OFTEN IN CAPS LIKE THIS!!!

I wish I could quote some of it here, but in the end the actual adjectival combinations are beside the point. What makes "The Cursing Mommy's Book of Days" so funny and true is not the language, but how the repetition of big absurdities makes little ones so absolutely unbearable, especially in domestic life.

Like the makeover of grocery stores into warehouses. "The place is now a truck terminal, basically," Cursing Mommy grumpily observes about her local market. As if all people need was stuff, not anything else that goes with obtaining it, like fellowship or courtesy.

There's a larger humiliation borne out here, one emblematic of our hyper-capitalist world. Anything that can be commodified will be, such as care. Cursing Mommy's father, who abandoned her and family, has moved into a later life facility. He is suffering from dementia, so even while he requires forgiveness he cannot be grateful for it.

"Cursing Mommy's Book of Days" may begin as a gag but it ends as a meditation on the gag that is midlife. Just when you reach the peak of your earning power and life should be at your feet, you find that your family, your parents and everyone else is lined up there instead, often accompanied by a mess to clean up. In this warm and deceptively political book, Ian Frazier gives us a chance to laugh at this dark truth before we dive back into it.

John Freeman is the editor of Granta and author of "The Tyranny of E-mail."