JUDITH ROSSNER has fashioned her career as a best-selling novelist by concentrating on fairly titillating topics: singles bars and brutal murder (Looking for Mr. Goodbar); the lives and loves of Siamese twins (Attachments); and the plight of a Lowell mill girl who winds up married to her own illegitimate son (Emmeline). Now in August, it appears --at first--as if we're in for more of the same. Dawn Henley, a beautiful, blond 18-year-old, arrives for a consultation with a New York analyst, Dr. Lulu Shinefeld, and, quickly, we're given the facts of the case. Dawn is an orphan. Her mother committed suicide when Dawn was six months old. Her father died in a boating accident a year later. Dawn has been raised by her Aunt Vera, a lesbian, and Vera's lover, a woman named Tony. Tony has now left the family and is married to a man in Boston. As a child, Dawn called Vera "Daddy" and Tony "Mommy" until she got to school and the teachers corrected her by making her recite drills about family structure. It's not surprising that the girl's life is a mess.

What is surprising, however, is that, despite the sensational circumstances of Dawn's early life, this is not just one more sensationalized novel. Rossner's new book turns out to be more careful and more contemplative than any of her earlier works--and, ultimately, far more satisfying. August takes its title from the vacation month that is traditional among New York analysts. For patients like Dawn Henley, the month is likely to be an expanse of blackness, a time of non- being. "Labor day," Dawn says. "When all the analysts come back to New York and give birth to their patients." But for the analysts themselves, of course, the month means something else entirely, and Rossner makes us privy to the world that Dawn Henley will never be allowed to see--Dr. Lulu Shinefield's August.

It is, in part, a month of East Hampton parties and days at the beach, drinking and casual flirtations. But, most of all, it is a month for the doctor who has sat in her office, composed, controlled and larger than life-- Dawn Henley imagines her to be a great deal taller than she really is--to be able to be herself, to make mistakes. In August, she is Lulu, twice-divorced, 40 years old, the mother of two young sons and a daughter, Sascha who has run away from home and is "lost" to her mother. In August, Lulu Shinefeld slips into a life that is almost as moving and messy as anything Dawn Henley has to offer.

Throughout the novel, Rossner allows us to shift focus from patient's story to doctor's story and back again. Over the course of five years, we follow the progress of Dawn's therapy and in the interludes--Augusts, Christmas vacations-- we tune back into Lulu Shinefeld's personal life. This device works especially well because Lulu and Dawn are good counterpoints, both physically and emotionally. From their separate positions, they hold the book in a kind of precarious balance that seems just right--there's just enough teetering to give it energy.

When Dawn Henley's "parents," Tony and Vera, split up, 13-year-old Dawn broke her neck in a bicycle accident. Years later, when her first analyst, a man who had become a father figure to her, announced that it was time to terminate her therapy, Dawn crashed her car and nearly killed herself. In her work with Dr. Shinefeld, the girl brings in a series of lithographs she's made: powerful pictures of loneliness, including an empty chair, dead flowers and the slats of a baby's crib, bathed in a cold yellow light. It's not hard for us to figure out that the root of Dawn's trouble lies in the early loss of her real parents--her "birth parents" as she calls them. As we look on, Dr. Shinefeld helps the girl move closer and closer to this truth and we get a good idea of just how delicate and how painful the process of analysis can be.

Rossner has taken great care to fill this novel with convincing details of psychoanalysis. Dawn's dreams and artwork, her fears and fantasies are all painstakingly recorded as are the "business" aspects of visits to a therapist--the buzzer in the waiting room, the exact position of the furniture in the doctor's office. Still, there will always be quibblers who aren't convinced. Anticipating this, Rossner prefaces this book with a crafty little disclaimer. "It would be useful," she writes, "to remember that the psychoanalysis that takes place within this novel bears approximately the resemblance to a real analysis that the novel bears to life." It might take even Lulu Shinefeld a while to analyze all the possibilities contained in that small statement. But, for most of us, it isn't really necessary. We're willing to go along with the story of Dawn's treatment because Rossner has created characters that we care about. It doesn't much matter if the facts don't all drop neatly into place. And it doesn't much matter that Rossner's prose is workmanlike and, on occasion, even clunky. This is a book that keeps us reading to the end because what does matter to us is what will become of these two women. The unraveling of Dawn's secrets and the ups and downs of Lulu's life are as absorbing as a good mystery story.

In the end, of course, unlike a mystery, there are no easy answers, no final solutions. "People don't get finished," Dr. Shinefeld tells Dawn. "They're not books or statues." Judith Rossner understands this well. At the end of August, she leaves us with a nicely drawn closing scene, a scene that is both so hopeful and so uncertain that we believe it entirely. It's the way life works. CAPTION: Illustration, jacket design from"August" By Fred Marcellino; Picture, Judith Rossner. Copyright (c) By Susan Oristaglio