"Coming Out . . . once it meant wearing a long satin train and tall feathers and curtsying to the Queen. Whereas now . . . Whereas now -- yes. The central character of this novel remembers another world, a world that must still exist somewhere, "in Basingstoke or Lincolnshire or Leeds," or maybe Duluth. It was a world in which "lady" was not a democratic genteelism for "woman"; still less did it suggest aristocracy or money. Rather it suggested the staunch decencies of those who'd had advantages, which conferred obligations, who were brought up with principles, eating good breakfasts, wearing sensible underwear and white gloves on the appropriate occasions.

They (substitute "we" if you're old enough) were brought up to go to bed at half-past seven, to be truthful, to be reliable -- in a world in which there was relatively little to be known about sex and in any case you didn't know it, and little girls could play in Hampstead Heath (or Rock Creek Park, or Central) without danger.

Now, a war and a generation later, Frances is 49, and she stands, in the words of one of those poems nobody remembers anymore, like Casabianca on the burning deck whence all but she have fled. She and Ruth and Jenny, the two plump middle-aged women who are her closest friends, seem secure enough. They still live in London NW4, where they grew up; their three neat pairs of boys and girls are healthy, bright and still in easy reach. But the certainties are gone.

Friend Jenny's daughter is photographed in feathers, indeed, but that's all she's wearing. At least she's not on welfare, like Ruth's Julian and Louise; Jennifer makes plenty, and her loyal parents display the feather photo, and the one in the black garterbelt, in the sitting room, "lest anyone should think [they] are in the last ashamed."

Jenny's Roger is the only one of the six to have imbibed the older generation's principled reliability. He has Come Out, and "although we are all fully behind all our children in all their campaigns . . . we do wish Roger's conscience would not lead him into such repeated and explicit statements." Julian's reliability is minimal, although you can count on locating him daily from 3 to 4 playing the guitar in the Marble Arch tube.

Louise practices meditation and granola; her mother catches herself asking whether she's done her TM yet. "How furious," notes Frances, "she'd have been if you'd asked if she'd said her prayers." Frances's own Jonathan is a militant squatter in a London town house, along with a few squalid poor and many squalid privileged; her Caroline has run off with her art professor, leaving behind his pregnant wife. And Frances herself -- dependable, open-minded, reasonable Frances, who misses her dead husband with an emotion she is too sensible and controlled to allow herself to acknowledge -- Frances has taken a lover.

Frances has performed miracles of adaptation. Sensitive as well as sensible, self-deprecating, humorous, highly intelligent, she watches herself fighting the good fight, pulling the children's chestnuts out of the fire when they need it and when they don't. She laughs. What else is there to do? Is there any behavior remaining that a reasonable, reliable, modern mother can't swallow.

It almost seems there is, as the novel progresses -- almost, but not quite. Catherine Heath's clear affection for the freckless young persuades us to believe that even such an exemplary cluster of kids might exist, illustrating every contemporary trend and testing every area of elasticity in their parents. "Lady on the Burning Deck" is a funny book and a very well-written one. Though many pages make you giggle, and some made me laugh aloud, it doesn't lurch from boff to boff. The book is about something. This is a warm comedy in which the verbal wit is at the service of the humor of situation. Things happen that are too funny to reveal. But the comedy, however broad, is suffused with a rueful tenderness that shadows what might otherwise be a mere summer afternoon's romp.

Take Alison Lurie's sharp eye (but not her sharp tongue), or equal parts of Erma Bombeck and Margaret Drabble, for there is seriousness amid the comedy, a consciousness of gain as well as of loss. The events of the novel change Frances; she too cannot remain what she was, though unlike, it seems, everybody around her, she retains the memory of the standards it was once possible to live by and the capacity to be shocked, not at others' deviations from them, but at her own. Heath's nostalgia is free of sentimentality, as are the rhythms of her prose:

"I think of the old Mississippi paddleboats in the films before the war, the films of my childhood. Sometimes I think we are all being swept down a river in flood on just such a boat. Our life goes on in glorious Technicolor; a band plays: we dance on deck. But every now and then I look longingly towards the riverside villages sweeping back into the black and white past; I gaze with passion at the distant banks, where stand the stable houses, where dwell the sober unsurprising souls."