INCE the 1999 film adaptation of her novel ''The Talented Mr. Ripley,'' Patricia Highsmith has been gaining posthumous celebrity. American fame evaded her during her lifetime. Her uncomfortable, slightly repellent novels of passivity, humiliation, delusion and futility skitter in a border zone between serious literature, pulp fiction, comic book and psychiatric case study. Charting Highsmith's inner life is a difficult job for a biographer; it seemed to baffle Highsmith herself. She often felt blank, unmoored and frightened. In her diary in 1951, she wrote: ''O who am I? Reflections only in the eyes of those who love me.'' The prospect of a biographer prompted anxiety and dread. She asked two friends to steer off the wrong ones. In ''Beautiful Shadow,'' Andrew Wilson achieves the detachment required to document Highsmith's bizarre personal habits (carrying a purse full of snails, obsessing over human waste disposal) while still appreciating the intellectual and emotional insights she had to give.

Both her intimate life and literary career followed an arc of rapid early rise and slow painful decline. Highsmith, born in Fort Worth in 1921 and raised in New York, was a beauty in her youth; she preferred women sexually, although she preferred men in all other ways. For six months in 1949 she made a futile effort to analyze and ''cure'' herself for her fiance, the novelist Marc Brandel. As it turned out, her private life would be a sexual picaresque. Among her American lovers Wilson names Virginia, Helen, Mary, Allela, Chloe, Natica, another Virginia, Ann, Kathryn, Lynn, Ellen, Mary, Marijane and Daisy.

Her early hopes for love are mirrored in ''The Price of Salt,'' her 1952 lesbian romance, published under a pseudonym. The elegant Carol, in mid-divorce, falls for a nervous shopgirl, Therese. They take a cross-country road trip. A private detective hired by Carol's husband bugs their hotel rooms. Forced to choose between custody of her daughter and her relationship with Therese, Carol chooses Therese. Carol incarnates Highsmith's romantic ideal -- dominant, slightly menacing, challenging, but nurturing enough to make Therese a cup of hot milk and put her to bed.

Marijane Meaker is best known for young-adult novels, written as M. E. Kerr, but also for thrillers (''Come Destroy Me'') and steamy lesbian romances, and a confessional style animates ''Highsmith,'' her sincere account of their relationship, which took place between 1959 and 1961. Highsmith is introduced drinking in a lesbian bar, looking ''like a combination of Prince Valiant and Rudolf Nureyev.'' She is 38 years old and published in cloth editions, not pulpy paperbacks -- a blue-chip stock in New York's chic lesbian circles. They sit down together. Meaker has read Highsmith's work; Highsmith has not read Meaker's. Meaker ditches her girlfriend, and they set up shop. Highsmith goes on book tour. The pair dines with Janet Flanner, novels are written and alcohol is consumed. For six months the two live together near New Hope, Pa. Highsmith is a lovely girlfriend: she squeezes orange juice in the morning and leaves a book of poetry on Meaker's desk, bookmarked by a leaf. This awkward, insecure alcoholic is not, however, the Prince Valiant whom Meaker expected. Meaker is frequently critical, disappointed, jealous and hostile. Finally Highsmith moves out.

Highsmith, who admitted to a strong masochistic streak, gravitated to a dark type -- older, dominating and belittling. Wilson reports that one lover, a fierce and punishingly superior sociologist named Ellen Hill, bossed her around like a governess. Highsmith always managed to extricate herself from these martinets but could never change her ideal.

Highsmith moved to Europe in 1963, in thrall to an Englishwoman. The shift cut her off from the elaborate social networks of New York's gay and literary worlds. She had a few love affairs: Madeleine, Marion and Monique. But in her last years, Highsmith switched to completely unrequited crushes on movie stars and, finally, Tabea Blumenschein, a 25-year-old actress in German experimental films, with whom Highsmith was obsessed for years after their brief fling in 1978. She was left entirely to her own devices for the last 30 years of her life, until her death in 1995. She ate sparsely and drank epic quantities, marking her Scotch bottle each morning to monitor her consumption. She became so stingy that she lugged an old pile of firewood from home to home, and drove 60 miles to buy cheaper spaghetti.

Wilson is less confident about Highsmith's creative life than her emotional one. She wrote 22 novels, beginning in 1950 with ''Strangers on a Train,'' memorably filmed by Alfred Hitchcock. (In 1961, he bought the rights to ''This Sweet Sickness,'' her painful novel about obsessive imaginary love.) She started writing because it helped purge anxiety and organize her vulnerable psyche. She continued out of her ambition to become a novelist of psychic conflict; her great hero was Dostoyevsky. Her books take hostility, guilt, anxiety and resentment, exaggerate them and project them into the world. Many of her protagonists tap us on the shoulder, reintroducing situations and emotions we would rather not admit knowing: David insists that he is loved when he is not; Howard can't decide whether he is responsible for someone's death, or whether he cares if he is. Some of her murderers (notably Guy in ''Strangers on a Train'') have guilt-ridden moral lives, but others (notably Tom Ripley) are blithely indifferent.

Her early, most chaotic and blood-soaked novels had cinematic locations and plotted thrills and chills yet showed subtle psychological insight. Highsmith empathized with the weak and humiliated and understood their attraction to violence. (She would dedicate novels to the Palestinians.) Later, she tried to capture the everyday psychic disarray of more balanced characters. The idea behind ''Edith's Diary'' (1977) is compelling and frightening: the horror lies in the punishing inertness of an abandoned housewife's disappointing life. Edith embodies self-protective delusions. After her husband leaves her, the timid woman begins to disintegrate. She keeps a secret diary in which she pretends that her son, a dateless, jobless jerk, is a Princeton-educated engineer with a wife and child. Highsmith buries the reader under descriptions of old coffee grounds, frozen macaroni and cheese, prescription bottles, newspaper clippings and dirty socks. Yet the characterization is thin. The novel is relentless and deadening but falls short of being affecting.

Increasingly depressed herself, Highsmith churned out four second-rate Ripley sequels and seven volumes of foul-tempered stories that were frightening only in terms of quality. American editors rejected her books. In an interview, she claimed that ''the nitty-gritty'' of life is ''anger and a sense of injustice.'' Previously a thoughtful, morally serious woman, she increasingly became a vocal racist and anti-Semite. (Highsmith read a negative review and wrote Meaker, ''If this is East Coast Jews hitting back, I can be only flattered.'') One friend claims that she found an equilibrium in writing: she could write increasingly bleak novels of disappointment and horrific stories of violent revenge. In the last years of her life, the current revival began -- The New Yorker published an appreciation of her work and the editor Gary Fisketjon took her on -- but the enthusiasm was for work that was 30 years old.

Wilson implies that while Highsmith's life was not perhaps joyous or exemplary, it had its own logic. But in the end, Highsmith seems a sad figure, a disappointment to herself. Resentment seeped out of her -- she hated Jews, women, taxes, literary agents and her mother's nursing-home bills -- yet she never exploded as her characters did. Her biography shows that hostility, frustration and loneliness can lead to a crushing life as well as a cathartic one.