"I'm not a writer who begins with ideas," says Maria Flook. "I begin with affliction -- the affliction of obsession." Flook's own affliction -- and the self-described source of her art -- is the disintegration of her family, which she chronicles in My Sister Life: The Story of My Sister's Disappearance (Pantheon). The book, which opens in 1964 and closes in the present, is not only a study of a childhood gone awry but also a meditation on the endeavor of balancing private pain with artistic activity. In one of its final scenes, Flook's older sister, Karen, 24 and a former child prostitute, discovers that Flook, a promiscuous 22-year-old pill addict and single mother, is applying to M.F.A. programs. Karen turns to her little sister and poses a harsh question: "You lead a double life, you know that? Which part is bullshit?"

Judging by her books and her life, the answer is neither. Flook's artistry and her experience exist in an intense symbiosis; donning an artist's objective eye permits Flook to keep a troubled past at bay.

In person, this dichotomy makes Flook something of a chameleon. A slender, conservatively dressed 45-year-old, she greets PW holding an immaculate manila envelope that contains her past reviews and a copy of her first volume of poems. Flook is the author of two novels (Family Night, 1993, which won a PEN American/Ernest Hemingway Special Criterion, and Open Water, 1995); a collection of short stories (You Have the Wrong Man, 1996); and several books of poetry. She has an anxious, watchful air that is countered by a raw, forceful speaking voice and an unassuming candor. Speaking with PW over dinner at a Provincetown, Mass., restaurant and, the following morning, at the home in neighboring Truro that she shares with her husband, John Skoyles, and 11-year-old son, Harry, she hopscotches among topics, giving her intellectual curiosity free reign. Her ebullience makes it easy to imagine why she grew impatient with the confines of poetry, her first literary calling ("I'm a storyteller. Poems don't give you enough elbow room.") As she mixes tales of schmoozing at a glitzy sales conference party last year with anecdotes of waitressing in strip clubs and scoring heroin (Flook has been sober and drug-free for a long time), she alternately suggests a less louche Marianne Faithfull and your favorite Woodstock mom.

Though she jokingly complains about magazine editors' requests for "tales of a junkie mommie," Flook's identification with -- and allegiance to -- America's fringe population is clear from both her persona and her work. Holly, the protagonist of Open Water, is a chambermaid living in Newport, R.I. On probation for setting fire to her ex-husband's bed, she falls in love with a thief and morphine addict modeled on one of Flook's ex-boyfriends. The short stories in You Have the Wrong Man are peopled by transvestites and adulterers, alcoholics and cons. "I write about people in peril, people struggling," says Flook. She does so with a bone-deep affection that is singular, outlining her knockabout characters' capers and quirks without judgment in her simple yet rich prose.

My Sister Life locates the source of Flook's anti-mainstream bent in her chaotic personal background, and in her close tie with Karen (Karen, who never graduated high school, is currently married and works at a casino in a city that Flook declines to identify). "The tragedy of my family's disintegration is the core source of my art sensibility," says Flook. "It made me a witness -- I began to notice the world from an artist's point of view, and that's what saved me." The book follows the two sisters from childhood into their mid-20s. Besides documenting their troubled home life, it describes the gradual emergence of Flook's artistic sensibility and also provides a portrait of a suburban culture buckling under the onslaught of the 1960s. In an unexpected twist, Flook narrates half of the memoir from Karen's perspective, describing her sister's fugitive life with a vividness and verisimilitude all the more startling because it is wholly imagined.

Flook seems to have relished the task of capturing her sister's droll, more plainspoken adolescent voice, although she admits it was a technical challenge. "I had to remember what it was like to be 14 -- Karen's got this real understanding, coupled with an innocence," she reports. "She has a lot of street savvy, and a lot of interior savvy -- it's an intelligence that's remarkable, that comes from austerity of living." To aid her, Flook drew on her decades of informal phone "interviews" with Karen and also on her sister's letters to her. "People are going to wonder how I could re-create my sister's voice with license," says Flook, who adds that she wrote the book "with more authority" than any book she had previously written. "I'm so impregnated with this story, it's almost like it's in my marrow."

Flook was born in Hamilton, Ont., in 1952, the second child of Ray and Veronica, pseudonymously surnamed Mitchell in My Sister Life It was the second marriage for both, and her mother also had two children from her previous union. Between the ages of two and five, Flook lived in Italy, where her father had an engineering job with Fiat. The sisters later grew up in the affluent surroundings of suburban Wilmington, Del., where Ray ran a successful industrial supply company.

In My Sister Life, it is Veronica who plays antagonist to Flook and Karen's twin protagonists. Flook portrays her mother as an exceptionally beautiful narcissist determined not to brook any competition with her daughters for her husband's affections. "Veronica's enterprising sexuality overwhelmed our individual goals and spilled into family matters. Her erotic aspect emerged in her every routine and came more naturally to her than maternal duty," writes Flook. Flook credits this coldness, coupled with her father's passivity, with triggering Karen's early flight into indiscriminate sexual liaisons and her premature departure, at 14, from home. When Karen returned after two years, Veronica had her institutionalized. In the wake of Karen's departure, Flook, who was 12 at the time, herself began to unravel. She became a juvenile delinquent and a drug user, as well as sexually active, imagining that she was following in Karen's footsteps: "Perhaps Karen and I were twinned in a pernicious mutation -- little remnants of her soul had entwined with mine -- like a grafted branch," she writes.

In high school, Flook began to write seriously and became involved in the antiwar movement. Seven of her poems were accepted in a Random House anthology of "disaffected young writers." At 17, after also being institutionalized by her mother, Flook fled home for Providence, R.I., where she married a graduate student (whose name she still carries) who fathered her first child, Kate, now 23 and working as a school teacher in Minneapolis. Flook also took a bachelor's degree at Roger Williams College. After the breakup of her marriage in 1977, Flook earned an M. F. A. in poetry at the University of Iowa Writers Workshop, where her fellow students included Jane Smiley, Jorie Graham and Sandra Cisneros. Flook found the workshop "inhospitable to young writers," but that adversity helped galvanize her own creative commitment. Following her graduation, she came to the Fine Arts Work Center in Provincetown, where she held a seven-month fellowship. "That was a big turning point for me," she recalls.

"It was such a nurturing community here, and this town in winter is so desperately beautiful, and also so empty, you can turn to your work with this nourishment outside, but also without distraction." At the Center, Flook also met Skoyles, a writer and college administrator, whom she describes as having "been very supportive of my writing life. He also has an incredible literary mind that I can draw upon." The two were married in 1984.

In early 1982, Flook sold her poetry collection Reckless Wedding to Houghton Mifflin, unagented, for an $800 advance, and it was published that fall. Ampersand Press, a small house affiliated with Roger Williams College, next published a collection of stories, Dancing with My Sister Jane (the title story is a fictional treatment of some of the material in My Sister Life). In 1984, she and Skoyles moved to Asheville, N.C., where Skoyles worked for the M.F.A. program at Warren Wilson College, and Flook taught English.

There Flook wrote the manuscript that became Family Night, which her then-agent, Cynthia Cannell, submitted to Pantheon editor Dan Frank on the recommendation of a friend. Frank's acceptance marked the beginning of an editorial collaboration that Flook describes in glowing terms. "Dan has been an incredible source of vision and nourishment to me. He doesn't flinch from my darkness and actually mirrors it with a different level of acute perception," she says. Since 1993, Flook has been agented by Kim Witherspoon.

My Sister Life is not the first work in which Flook has raided her family background for creative material. The figure of a vanished older sister has appeared previously in numerous stories and poems, and fragments of dialogue from her other books resurface, verbatim, in My Sister Life ("It's because it's been percolating in my mind all this time," explains Flook, who was unaware of the cannibalization before it was pointed out to her). The father-obsessed half-brother of the protagonist of Family Night was so closely modeled on her real half-brother, Alex, that he didn't speak to her for two years following the book's publication.

"My allegiance to my writing is stronger than any family tie I might have, except for with my young son," responds Flook when asked if she feels any guilt over making public her siblings' personal histories. "And it's not my doing. I don't decide what to do as a writer-it gets me." She reports, clearly pleased, that her sister's response to My Sister Life has been positive. "She's told me what a relief it is not to have to live alone with her story. It vindicates her that her story was important enough to put on a page," says Flook, who gave Karen a sizable portion of her $90,000 advance for the book. Her mother, who currently lives in a retirement community in Wilmington and is in frail health, has not yet read My Sister Life.

Flook is excited at the advance buzz surrounding My Sister Life but irritated that it is being compared to such other familial tell-alls as Kathryn Harrison's The Kiss. "It makes my editor and me really nervous. We wish this whole memoir craze would disappear and people would just look at it as a book. It has a much broader canvas -- it's a portrait of an entire family, as well as of an era."

Flook, Skoyles and Harry settled in Truro in 1992, in a two-story house surrounded by scrub pines on the crest of a sandy hill, a 10-minute walk from the sea. There Flook writes for six or seven hours a day, three and a half weeks per month. During the fourth week, she critiques student work for the graduate writing seminars in the Bennington College M.F.A. program. The walls of her sun-drenched study, on the second floor of her house, are hung with pictures of her family and herself; behind her writing table is a neatly arranged bookshelf of her "research books." In the summer, she swims, takes her son's Labrador retriever, Chowder, for runs in the surrounding moors, and tends her garden. It's the kind of tranquil environment that seems ideally suited to permit the risky personal excavation work that Flook is called to undertake, both for the sake of her art and to achieve the emotional catharsis that she says brings her a measure of peace. "When I write about the past from the relative safety of my desk, I re-experience it, but within the cushioning framework of being an artist," she says. "I can't escape from my subject, because it comes from within, but I can find solace by addressing it as art.

"I'm interested in people who leave their safety zones in search of transformation," she continues. "You can't experience transformation without danger." Where willingness to face risk is concerned, Flook certainly seems ably endowed; it is this fearlessness that allows her to transmute family sorrow into literature, and to create an identity for herself supple enough to contain all her complexities.