Three Women at the Water's Edge, by Nancy Thayer. New York: Doubleday. 370 pp. $14.95. It is a real pleasure to see a young writer develop her craft from one work to the next. So often a first novel can have the freshness and immediacy of autobiographical detail; yet in the second and third, the meagerness of talent will betray itself in vaguely drawn characters and lackluster plots.
Nancy Thayer's first novel, ''Stepping,'' about the joy and pain of stepparenting, motherhood, and a woman's professional aspirations, had the vivacity and passion of a private diary-cum-writer's-notebook. It captured some of the elemental female experience found in Adrienne Rich's nonfiction study of motherhood, ''Of Woman Born.''
But ''Stepping'' also contained hilarious Erma Bombeck-ian flashes, wonderful comic scenes of the caterwauling maelstrom of a household full of infants. And it had the exquisite painterly touches of a Mary Cassatt, capable of evoking the warm pleasure of a mother hugging her fat, sweet baby.
Happily, Thayer's second novel, ''Three Women at the Water's Edge,'' has the same liveliness and believability of character, and yet it is an even better novel - more complex, more evenly paced, and the language more finely honed.
Without lapsing into rhetorical posturing or social cliche, Thayer's ''three women'' could stand for three of the common situations in which women often find themselves today. The transitions of modern life form the theme of this absorbing story of a mother and her two daughters.
The eldest, Daisy, pregnant with her third child, finds her domestic tranquillity shattered when her husband announces he is leaving her for a younger, ''professional'' woman. Daisy must face the truth that she has let herself go over the years: She has become fat, complacently sloppy, and intellectually lazy; she has withdrawn from her husband to the point where they regard one another with a kind of of benign neglect. But overnight, she is faced with the jolting prospect of raising three small children alone.
Her younger sister, Dale, proud of her self-sufficiency and her competence as a teacher, falls suddenly and violently in love. But even as she is thrown off balance by the man, Hank, she resists love, made fearful and suspicious of the whole process by her mother's and sister's disintegrating marriages.
Margaret, whom both young women regard as a good old Midwestern mother, rotund, gray-haired, and frumpishly solid, has painfully broken her 30-year marriage, in exasperation. Her husband adamantly refused to let her change her life in even such small ways as losing weight, or engaging in some cultural pursuits rather than playing bridge.
It wasn't Margaret, the woman, he wanted, but the perfect, unthreatening prop for a small-town businessman. Both husband and daughters wanted her to be an inexhaustible source of cookies, emotional Band-Aids, and domestic comforts - but not to let her intellect or her spirit show.
But that papier-mache prop has turned suddenly into a three-dimensional woman , to the shock of both daughters, as well as her former husband. Midwestern Margaret, at 50, has resurfaced as a new person - her own person - far out of reach in Vancouver.
Slim, stylish, intellectually vigorous, she lives in a glass-walled house at the edge of the ocean, has friends, even a handsome, sophisticated beau her own age.
The author does not romanticize or gloss over Margaret's choices; Thayer chronicles her pain, the effort and self-discipline it has taken to reach this point, and the sense of mourning at so many lost years, as Margaret, like so many late-middle-aged women today, sees the startling new freedom and range of opportunities opening to her. But she has character; she refuses herself the debilitating luxury of self-pity and launches vigorously into her new life.
Worst of all, in Daisy and Dale's opinion, she is cheerfully, unapologetically no longer the doughy matron they can turn to with their tears and wounds.
It is not that Margaret has turned her back on them; indeed, she writes her daughters outright love letters - full of her love for them and for her newfound life. These letters are one of the delights of this novel, which provide a marvelous portrait of a woman in full stride:
''Each morning I awaken,'' Margaret writes, ''to the dazzling bright splendor of sunlight on water, and I lie in bed watching the long, serious slender freighters glide past, and I try to think of the proper names for all the different blues I see dancing in the water. (Robin's egg, indigo, sapphire, mauve.) . . . At night it is the same. I cannot bear to go to sleep . . . I stare and stare out the window at the water, . . . Sometimes the moon spreads itself across the water in uneven, uneasy strips; it is always shimmering, changing, curving into new forms, as if lying very lightly and restlessly on the surface of the water, . . .'' Margaret feels she is ''living inside a rainbow, and everything is shimmering and iridescent and fine.''
She invites her daughters to visit her, in effect, to meet their new mother. But, because her Daisy and Dale are at turning points in their own lives, they refuse, bewildered by Margaret's changes. They'd prefer to crawl back into a plump gingham lap.
But Margaret's musing on the moon turns out to be more apt than her daughters would have supposed. They, too, are changing, and eventually they will find within themselves strengths they didn't know they had. And their own metamorphosis is brought about partly through the ''unmotherly'' but radiant new image of Margaret.
The moon has many forms and aspects, and so does motherhood, some of them altogether unexpected.
One looks forward to Nancy Thayer's third novel, already in progress, and the artistic growth, the curving new forms it will take.