By Rosamunde Pilcher

Thomas Dunne/St. Martin's. 530 pp. $19.95

"The Shell Seekers" is being billed by its publisher as a "family novel," which in this day of big books usually means a romp through three or four generations of a single family, who straggle on by, making money, love and trouble. The characterizations are shallow, plots implausible and the sex more ludicrous than lascivious as the poor, desperate author tries to invent new positions to amaze the blase' reader. Fun to read of a winter night; by morning one has forgotten who it was who did what to whom.

The reason the reader suffers instant amnesia is that the author has ignored the fact that plot comes from character -- that things happen to people because of who they are. Rosamunde Pilcher knows this and her book is not really a "family" novel but a novel about one woman, Penelope Keeling, and her relationship to her children.

Penelope Keeling is one of those people blessed with the ability to find happiness in life; when the big things collapse, she turns to the small, taking pleasure in giving friends a good meal or finding, in her winter garden, "snowdrops thrusting through the mossy turf beneath the chestnut, and the first butter gold petals of the aconites."

She loves her children but assesses them without sentiment: Her oldest daughter, Nancy, is a social climber whining her way into middle age; the middle child, Olivia, has pushed everything out of her life but the career she adores -- love, for her, must come in small doses. The beloved son, Noel, is a twister, using charm to implement his unlikely schemes.

Penelope is the embodiment of the perfect mother -- a bohemian who creates a warm and exciting environment for her children, despite a runaway husband and a lack of money. But perfection, like beauty, lies in the eye of the beholder, and only Olivia is satisfied with the casual, loving flamboyance of the eccentric Penelope. For Nancy, the perfect parent would have been a blue-haired dowager with correct connections. For Noel, it would have been a mother blind to his flaws who was happy to bankroll his schemes. These two, dealt a mother the world called perfect, feel sadly used.

The novel centers on the discovery by the two irritated and irritating offspring that artworks Penelope Keeling inherited from her painter father are now worth a great deal of money. If Penelope were to sell, Nancy could have the money to provide posh and proper schooling for her two unattractive children; if Penelope were to sell, she could give the money to Noel so that he could get rich quick.

One of the works is "The Shell Seekers." It is not just a valuable painting; it is Penelope's comfort and stability, reminding her of happy summer days in Cornwall when she not only gave love but got it back. Now her heart is under attack. Noel and Nancy nag her for money, flay at her as a failure.

And if the heart as the center of love is failing, so is the heart as the center of life. She denies the doctor's diagnosis of heart attack, but there is the shortness of breath and the tight band that pulls across her chest. She must take it easy, she is told. She must have a gardener. She must have a companion. And when they come, the young gardener and the even younger companion, they return her to a world where love is taken as offered, not handed back by a fussy recipient who insists that it be repackaged.

Pilcher's novel rests on a small, gentle plot about an aging woman coming to terms yet again with a less than perfect life. Everything about the novel is gentle, from the low-key writing to the understated humor, as when Penelope, on her wedding day, is asked by her new mother-in-law to "call me Marjorie":

"Penelope blinked in some astonishment. It seemed a funny thing to call your mother-in-law Marjorie, when you knew perfectly well that her name was Dolly." Nevertheless the obliging Penelope spends a year beginning letters, "Dear Marjorie." "It was not until many months had passed, by which time it was too late to rectify the situation, that she realized that Dolly had really said, in the foyer of the Ritz, 'My dear, I should like you to call me Madre.' "

It is just such silly misunderstandings that make up life and derail love, and Pilcher's book is a story about all the steps of love, from the first flush of gratitude at finding a winter aconite specking the snow to the awe of discovering another person whose life fits into your own. There are no complex ideas or complicated events. And there are no trapezes set up in the bedroom so the characters can astound the reader with high-flying feats. "The Shell Seekers" is about ordinary people doing ordinary things, and Pilchard has made that seem every bit as important as it really is.

The reviewer is a Washington writer and critic.