There are no wicked stepmothers in "Stepping." Instead, in Nancy Thayer's benign, cheerful novel, the heroine is loyal and eager, her husband patient and warm, and it's only her stepdaughters who refuse to do housework or sullenly stare at the people they should love.

"Stepping" follows Zelda Campbell's rocky course as stepmother to two adolescent girls, and it charts her personal growth as a woman who marries early, willingly accommodates herself to her husband's career and daughters, and, at 34, feels dissatisfied with the pleasant life that has nonetheless failed to advance her own teaching career. Her musings on her current lonely restlessness take place in Finland, where husband Charlie's on a year's Fulbright; they alternate with flashbacks of summers spent with Caroline and Cathy, along with disquieting phone calls from their angry mother Adelaide.

Charlie's daughters are confused and hurt by his divorce and remarriage, mixing tantrums and moodiness with a growing affection for Zelda. She tries extravagantly to please them, suppressing with humor her own hurt and frustration at their failure to love her and the subtle stubborness they display. On the surface they are all polite yet Zelda says, "It might have been better, that first year, if the girls could have arrived with whips . . . Their anger might have exploded and used itself up instead of burning along steadily . . ."

But the people in "Stepping" rarely admit their anger. It's as if there were faulty wiring running through the book so that just when the characters should be angry or demanding or despairing in a situation, completing themselves as characters, zap, there's a short circuit, and they are nice instead. When Cathy and Caroline, hostile at Zelda's pregnancy, refuse to acknowledge it, she also keeps silent, although "it was . . . a joyful part of my life, and I hated pretending otherwise." When they fail to help her clean or cook, she "felt a balloon of rage well up," but "it was easier to carry the laundry than to cope with the rage."

This tendency to suppress and accommodate marks the male characters as well. Stephen, Zelda's would-be lover, flies to Helsinki to declare his passion, miraculously hands her the teaching job she craves and, when she apologizes for refusing to sleep with him after grappling hotly on the bed, assures her, "I don't want you to sleep with me out of gratitude. Or out of boredom, or out of confusion, or out of anything else than love . . . It was worth it just to see the look on your face when I told you about the job."

Husband Charlie is the sort of sympathetic, wise, calm man who substitutes bland understanding for active support. Zelda tells us he's good in bed, attractive to other women and sought-after as an expert in the unnamed field of history he teaches, but we never see Charlie do anything or show an emotion stronger than bemused irritation or brief hurt. He remains undeveloped as a character, a faceless counterpoint to the emotional upheavals of his women, tolerant even of the ex-wife who harasses him.

There is an old-fashioned quality about Charlie, as there is about Zelda, despite her newfangled desire to find self-fulfillment through a job she enjoys. Not so Adelaide, in the opposite situation, a traditional woman wanting only home and family, unwillingly divorced, whose bitterness and melodrama give zest to the book. Adelaide has spunk. Despite herself she manages to pull out of depression, become strikingly successful at her job and remarry. Her progress says a lot for adversity in fostering growth, and not much for getting ahead if you're married to Charlie.

"Stepping" would benefit from more of the kind of tension an Adelaide brings to it. Fiction is charged by passion and conflict, given resonance and meaning. Fiction, in fact, makes possible the clear presentation of the very conflicts, muddied and suppressed, that hurt us in life, so that we can learn from the gains made by characters in handling the full range of their emotions. Zelda going crazy with frustration and boredom in Helsinki is a richer Zelda than the forgivinig stepmother, lively and amusing though she may be. And Zelda is best as the complex, loving, angry mother of her own young children, who can scream at them, then write with lyrical insight: "I won't know how to endure it when I don't have all this voluptuous, creamy, smooth, silky, perfect flesh to wash and clothe and hold and kiss and smell and see . . . I'll have to raise horses, dogs, cats, flowers; I'll have to have beautiful fabrics . . . to surround myself with cold beautiful artifacts to endure the sensual deprivation of my warm living babies."

Zelda is, in short, serious about her children, convincing us that they matter. It is harder to believe she really cares about the job she says is essential, since she describes no teaching scenes, takes no action to secure employment. Her goals and expectations simply don't seem that difficult to achieve. The choice between, or balancing of, family and career has become the classic woman's problem of the '70s, but one so commonly discussed in contemporary literature that it has lost dramatic impact as a theme in itself. In "Stepping" its treatment is far too modest, offering both Zelda and the reader less challenge than they deserve.