MOTHERS CAUSE PROBLEMS. Everybody knows that. They tell us what to wear. They make us practice the flute. Or they spend their days at the office so that instead of coming home to cookies and milk we come home to dinner defrosting on the counter. Anne Cameron, the 16-year-old heroine of A Formal Feeling, responds to her roommate's question about why she is unhappy, "It's my mother," and her roommate answers, "Oh, no wonder. I get in a foul mood every time I talk to mine." A natural response. Everybody knows mothers cause problems.

But that is nothing compared to the problems they cause when they are gone.

The Two-Thousand-Pound Goldfish and A Formal Feeling, two new novels for young adults, explore with sensitivity and skill the pain and problems of coming to terms with an absent mother. In Betsy Byars' Goldfish, Warren Otis constantly longs for the mother he has not seen in three years, since she started hiding from the FBI. In Zibby Oneal's novel, Anne's mother has died and, a year later, she has still not adequately mourned her or allowed herself to express the strong and painful feelings that will allow her to resume a normal life.

Anne returns home from boarding school for the Christmas holidays locked in a kind of bubble that separates her from her family and friends. She imagines herself on one side of a piece of glass, with everyone else on the other. Everything she sees and does seems strange, disconcertingly familiar, yet utterly changed. The biggest change is her new stepmother, a cheerful, casual woman very different from Anne's perfectionist mother. This difference, and the changes in the household, are accented by carefully observed details: breakfast dishes left in the once tidy sink, dyed carnations in the vase Anne's mother alway filled with eucalyptus leaves.

Instead of trying to accept these changes, or the kindness and interest of her family, Anne insists on idealizing her mother. She takes refuge in long-distance running and ice skating to escape from painful thoughts. At lunch with her brother, who tries to convince her that life must go on, "She would have liked to be running. . . . She imagined landscape spread beneath her feet like a map, and her legs, moving easily, carrying her away from the discomfort feathering at the edges of her mind." But eventually, through a series of flashbacks, she brings to the surface her real problem with her mother's death: anger at her mother for the demands she placed on Anne to be perfect and for the way she dominated her interests and tastes, and Anne's guilt at this anger and fear that she didn't love her mother at all.

Anne, though reserved and difficult, is not self-pitying. She is so human and so in need of loving that she is sympathetic and engaging from the beginning, and the other characters balance her with a warmth that is genuine and free of sentimentality. A Formal Feeling is straightforward, absorbing, and perceptive, true to an adolescent's feelings about mothers and about grief.

The Two-Thousand-Pound Goldfish is also perceptive, the story of a boy's need for love. Warren Otis is similar to Anne in one essential way. He, too, idealizes his mother, as well as the reunion he envisions between them. She is wanted by the FBI for politically motivated bombings, and he imagines her both as a wonder-woman avenger and as a loving mother who spends all of her time thinking about him and who will erase all his loneliness as soon as she returns. In fact, as his older sister points out, his mother did not spend much time with them when they were together, and the life she chooses to live does not center on them.

Warren denies such painful facts by inventing horror movies so vivid to him he can forget the loneliness of his days. The 2,000-pound goldfish is one such fantasy, once flushed down a toilet, exposed to dangerous waste material, now forced to slurp the human beings who cross his path to live. Yet even though the goldfish devours sewer workers and stray dogs, there is something gentle and appealing about him. He is the perfect counterpart to Warren, whose life is also shaped by things he cannot control, and who is gently heroic as he keeps believing in his mother.

When Warren learns that his mother sometimes calls his sister, and has also been in town without meeting with him, however, he must rethink the picture he has of her. For the first time he admits both anger and disappointment. "Suddenly Warren was overcome with the wish that he had a mother who didn't care so much about the world. . . . He wanted one of those mothers he saw . . . standing in line to have their children's pictures made, the children as clean and combed as if they'd just come out of a box." This poignancy is intensified when Warren finally gets to speak to his mother for a few minutes. Should he tell her about his friend or his grades? "These were things you told your mother every day when you got home from school, things you told at the kitchen table while you were having cookies and milk. Tonight he had to tell his mother something so interesting, so fascinating she would not want to hang up. . . ." This conversation helps Warren to accept his mother's absence, and to understand more realistically her character and her feelings.

Through such sensitive observations about a child's need for ordinary life and love, Byars turns an unlikely and grim situation into a moving and sometimes humorous story. Like A Formal Feeling, The Two-Thousand Pound Goldfish is a novel that gracefully expresses serious themes. Both these books deal honestlyywith the longing in all of us for the ideal mother, and with the consequent disappointment, anger, and acceptance that is part of growing up.