Home Is Where the Heart Breaks : WE WERE THE MULVANEYS.<i> By Joyce Carol Oates (Dutton: $24.95, 432 pp.)</i>

Families do come apart. Good, solid families, and for all kinds of reasons. Death, drink, betrayal, a sudden reversal of financial status, a whisper of scandal. . . . Some unthinkable thing happens, after which--or so the story goes--nothing is ever the same again. Houses go dark, weeds run rampant, the daytime drinking begins. There, family members tell themselves and others, pointing at calendars, scrapbooks or a photograph, it happened right there.

“We Were the Mulvaneys,” Joyce Carol Oates’ 26th novel, tells the story of such a defining moment in a family’s life. Set in a remote and windy spot in rural upstate New York, the book begins wistfully, “We were the Mulvaneys, remember us?” and then goes on in this nostalgic tone, recounting other and better times, as if of people a generation or so dead and gone. “For most of my childhood as a Mulvaney . . . ,” our narrator, Judd Mulvaney states, “I was the baby of the family.” As if that fact didn’t hold true anymore and hadn’t for a long time, even though Judd Mulvaney is only 30 years old and is speaking of events that happened to himself and his mother, father and siblings. As if even his position in the family had been blotted out by circumstance and reputation.

A newspaperman, Judd says he is telling his family’s story because he wants to “set down what is truth.” He will, he promises, include as many hard facts as he can come up with, but “ . . . the rest is conjecture, imagined but not invented . . . based upon memory and conversations . . . about things I had not experienced firsthand . . . .” Judd is, in a word, Oates’ alter ego, the perfect fiction writer, making imaginative speculations based on research, experience and careful thinking. The book won’t be a confession, Judd assures us, but a family album. “. . . If you’ve been a child in any family you’ve been keeping such an album in memory and conjecture and yearning, and it’s a life’s work, it may be the great and only work of your life.”

Throughout her long and staggeringly impressive career, Joyce Carol Oates has performed many a surprising quick-change imaginative shift. In “We Were the Mulvaneys,” she veers dramatically away from the voice, tone and subject matter of her recent urban horror stories (“What I Lived For”; “Zombie”) to write a completely heartbreaking farm-life novel about the dreams, aspirations, decline and readjustments of a close-knit, purely American family whose illusions and self-assessments are challenged by a brutal event they can neither fathom nor confront, much less transcend.

Judd Mulvaney sets up his story with an appropriate who-what-when-where newsman’s introduction. A handsome roofer, Michael Mulvaney and his slightly daffy and appealingly slapdash young wife, Corinne, live with their four children in a three-story lavender house, far from town in an isolated spot on a high hill where the wind always blows. Michael has his own business in town. He and Corinne work hard to make a decent life for themselves and to educate their children and succeed by the standards of the community.

Their first child, Mike Jr., born in 1954, becomes the all-around athletic pure boy. The other children appear in quick succession: Patrick, the family’s straight-A science student and intellectual; Marianne, the perfect girl--solid Christian, cheerleader, uncomplaining, sweet and selfless; and Judd, the tag-along baby. It’s one of those wildly alive and wonderfully messy households in which activity, genuine warmth and a lot of pure noise often serve as a substitute for real intimacy. There are dogs, cats, goats, birds, horses, slogans, nicknames--the self-sustaining and defined world of a large family living in the country.

”. . . The Mulvaneys,” Judd Mulvaney tells us, “were a family in which everything that happened to them was precious and everything that was precious was stored in memory and everyone had a history.” Until, that is, 1976, “when everything came apart for us and was never again put together in quite the same way.”

It’s Sunday, 1976, the day after Valentine’s Day. There’s a phone call from town. Seventeen-year-old Marianne needs a ride home. Having been chosen to be in the court at the Valentine’s prom held the night before, Marianne had spent the night with a friend. For some reason, her date is not bringing her home as planned. Without asking questions, Corinne sends Patrick to get his sister. The chapter begins, “No one would be able to name what happened, not even Marianne Mulvaney, to whom it happened.”

Unlike the busy, talkative Mulvaneys, the reader immediately suspects what has happened to Marianne: She has been raped. Oates doesn’t take long to confirm that awful fear as Marianne washes her ruined gown in the sink, stores it in the back of her closet, and goes on. Or tries to. In complete aloneness, she does what good girls are trained to do: shines the light of blame on herself.

In time, the Mulvaneys get it. Then what? How does a family adjust to the dreaded, unthinkable thing? How do they right the balance, grab back their life, make it the way it was? The rest of the book grapples with these questions and explores the ways different members of the Mulvaney family deal with them. The men in the family want revenge. In the end, however, they aren’t up to the kind of violence they expect of themselves. Nobody knows what to do and so nobody, in truth, does anything. The family starts to feed on itself. The book covers the next 17 turbulent, sometimes awful, years of the lives of the Mulvaneys, as each one tries to patch together a new self, apart from the family.

Joyce Carol Oates is just a fearless writer. Where others tremble and falter, she plunges right in and does not look up or come to shore until the fullest telling of the tale, the most thorough examination of the direst possibilities, the most exacting testing of ordinary assumptions and theories, have been played out. “We Were the Mulvaneys” is yet new testimony to her great intelligence, certainly, but, more important, to her brave heart and her impossibly lush and dead-on imaginative powers. On a more immediate and emotional level, it’s an extremely generous book about the limits of love and responsibility. It is a book that, because it fulfills its promise to “set down what is truth,” will break your heart, heal it, then break it again every time you think about it.