Truman Capote, one of the postwar era's leading American writers, whose prose shimmered with clarity and quality, died yesterday in Los Angeles at the age of 59. Mr. Capote died at the home of Joanna Carson, former wife of the entertainer Johnny Carson, in the Bel-Air section, according to Comdr. William Booth of the Los Angeles Police Department. ''There is no indication of foul play,'' he said, adding that the county coroner's office would investigate the cause of death. The novelist, short story writer and literary celebrity pioneered a genre he called ''the nonfiction novel,'' exemplified by his immensely popular ''In Cold Blood.'' He died apparently without having completed his long- promised ''masterwork,'' an extensive novel called ''Answered Prayers.'' Mr. Capote's first story was published while he was still in his teens, but his work totaled only 13 volumes, most of them slim collections, and in the view of many of his critics, notably his old friend John Malcolm Brinnin, he failed to join the ranks of the truly great American writers because he squandered his time, talent and health on the pursuit of celebrity, riches and pleasure. ''I had to be successful, and I had to be successful early,'' Mr. Capote said in 1978. ''The thing about people like me is that we always knew what we were going to do. Many people spend half their lives not knowing. But I was a very special person, and I had to have a very special life. I was not meant to work in an office or something, though I would have been successful at whatever I did. But I always knew that I wanted to be a writer and that I wanted to be rich and famous.'' Success, both as a writer and as a celebrity, came early, when he was 23 years old and published his first novel, ''Other Voices, Other Rooms.'' It was a critical and financial success, and so were most of the volumes of short stories, reportage and novellas that followed, including ''Breakfast at Tiffany's,'' ''The Muses Are Heard,'' ''The Grass Harp,'' ''Local Color,'' ''The Dogs Bark'' and ''Music for Chameleons.'' But the book that perhaps solidified his claim to literary fame was ''In Cold Blood,'' his detailed, painstakingly researched and chilling account of the 1959 slaying of a Kansas farm family and the capture, trial and execution of the two killers. Published serially in The New Yorker and then as a book in 1965, ''In Cold Blood'' consumed more than six years of his life. But it won him enthusiastic praise, mountains of publicity, millions of dollars and the luxury of time to work on ''Answered Prayers.'' But he accelerated the speed of his journey to celebrity, appearing on television talk shows and, in his languid accent, which retained its Southern intonation, indulged a gift for purveying viperish wit and scandalous gossip. He continued to cultivate scores of the famous as his friends and confidants, all the while publishing little and, he said later, developing a formidable ''writer's block'' that delayed completion of ''Answered Prayers.'' To keep alive the public's interest in the promised work, in 1975 he decided to allow the magazine Esquire to print portions of the unfinished novel. The decision was catastrophic to the grand social life he had cultivated because, in one of the excerpts, ''La C^ote Basque,'' Mr. Capote told apparently true and mostly scandalous stories about his famous friends, naming names, and in so doing forever lost their friendship and many other friendships as well. Soon his long-simmering problems with alcohol and drugs grew into addictions, and his general health deteriorated alarmingly. The once sylphlike and youthful Mr. Capote grew paunchy and bald, and in the late 1970's he underwent treatment for alcoholism and drug abuse, had prostate surgery and suffered from a painful facial nerve condition, a tic doloreux. In ''Music for Chameleons,'' a collection of short nonfiction pieces published in 1980, Mr. Capote, in a ''self-interview,'' asked himself whether, at that point in his life, God had helped him. His answer: ''Yes. More and more. But I'm not a saint yet. I'm an alcoholic. I'm a drug addict. I'm homosexual. I'm a genius. Of course, I could be all four of these dubious things and still be a saint.'' Named Truman Streckfus Persons after his birth in New Orleans on Sept. 30, 1924, he was the son of Archulus Persons, a nonpracticing lawyer and member of an old Alabama family, and of the former Lillie Mae Faulk, of Monroeville, Ala. Years later he adopted the surname of his stepfather, Joe Capote, a Cuban-born New York businessman. Mr. Capote's mother, who eventually committed suicide, liked to be called Nina and was not, according to her own testimony as well as her son's, temperamentally suited to motherhood. Living with her husband in a New Orleans hotel, she sent Truman to live with relatives in Monroeville when he was barely able to walk, and for the first nine years of his life he lived mostly in Alabama under the supervision of female cousins and aunts. In that period, he said years later, he felt like ''a spiritual orphan, like a turtle on its back.'' ''You see,'' he said, ''I was so different from everyone, so much more intelligent and sensitive and perceptive. I was having fifty perceptions a minute to everyone else's five. I always felt that nobody was going to understand me, going to understand what I felt about things. I guess that's why I started writing. At least on paper I could put down what I thought.'' Most summers the boy returned to New Orleans for a month or so, and accompanied his father on trips up and down the Mississippi aboard the riverboat on which Mr. Persons worked as a purser. Truman learned to tap dance, he said, and was proud of the fact that he once danced for the passengers accompanied by Louis Armstrong, whose band was playing on the steamboat. Many of his stories, notably ''A Christmas Memory,'' which paid loving tribute to his old cousin, Miss Sook Faulk, who succored him in his childhood loneliness, were based on his recollections of life in and around Monroeville. So were his first published novel, ''Other Voices, Other Rooms,'' his second, ''The Grass Harp,'' and the collection of stories, ''A Tree of Night.'' The young Truman's best friend in Monroeville was the little girl next door, Nelle Harper Lee, who many years later put him into her Pulitzer Prize-winning novel, ''To Kill a Mockingbird,'' in the character of the precocious Dill Harris. (He had earlier used Miss Lee as the prototype for the character of Idabel Tompkins in ''Other Voices, Other Rooms.'') After his mother's divorce from Mr. Persons and her marriage to Joe Capote, she brought her son to live with them in New York. He was sent to several private schools, including Trinity School and St. John's Academy in New York, but he disliked schools and did poorly in his courses, including English, although he had taught himself to read and write when he was 5 years old. Having been told by many teachers that the precocious child was probably mentally backward, the Capotes sent him to a psychiatrist who, Truman Capote said triumphantly some years later, ''naturally classified me as a genius.'' He later credited Catherine Woods, an English teacher at Greenwich High School in Connecticut, with being the first person to recognize his writing talent and to give him guidance. With her encouragement he wrote poems and stories for the school paper, The Green Witch. He did not complete high school and had no further formal education. At the age of 17, Mr. Capote wangled a job at The New Yorker. ''Not a very grand job, for all it really involved was sorting cartoons and clipping newspapers,'' he wrote years later. ''Still, I was fortunate to have it, especially since I was determined never to set a studious foot inside a college classroom. I felt that either one was or wasn't a writer, and no combination of professors could influence the outcome. I still think I was correct, at least in my own case.'' In a two-year stay at The New Yorker, Mr. Capote had several short stories published in minor magazines. ''Several of them were submitted to my employers, and none accepted,'' he wrote later. In the same period, he wrote his first, never-published novel, ''Summer Crossing.'' Mr. Capote made his first major magazine sale, of the haunting short story ''Miriam,'' to Mademoiselle in 1945, and in 1946 it won an O. Henry Memorial Award. (There were to be three more O. Henry awards.) The award led to a contract and a $1,500 advance from Random House to write a novel. Mr. Capote returned to Monroeville and began ''Other Voices, Other Rooms,'' and he worked on the slim volume in New Orleans, Saratoga Springs, N.Y., and in North Carolina, finally completing it on Nantucket. It was published in 1948. The novel, a sensitively written account of a teen-age boy's coming to grips with maturity and accepting his world as it is, achieved wide popularity and critical acclaim and was hailed as a remarkable achievement for a writer only 23 years old. In 1969, when ''Other Voices, Other Rooms'' was reprinted, Mr. Capote said the novel was ''an attempt to exorcise demons: an unconscious, altogether intuitive attempt, for I was not aware, except for a few incidents and descriptions, of its being in any serious degree autobiographical. Rereading it now, I find such self-deception unpardonable.'' The book's back dust cover received almost as much comment as the novel itself, and for years was the talk of the literary set. The jacket was a photogragh of an androgynously pretty Mr. Capote, big eyes looking up from under blond bangs, and wearing a tattersall vest, reclining sensually on a sofa. The striking, now-famous dust-jacket photograph may have been prophetic, because Mr. Capote, for the remainder of his life, assiduously sought personal publicity and celebrity and said he had ''a love affair with cameras - all cameras.'' In the pursuit of literary celebrity in succeeding years, the writer was photographed in his homes in the Hamptons on Long Island, in Switzerland and at United Nations Plaza. He was photographed escorting well- dressed society women who seemed always to tower over Mr. Capote, who was only 5 feet 4 inches tall. He was also photographed, for dozens of magazines and newspapers, when he gave a much-publicized masked ball at the Plaza Hotel in New York in 1966 for some 500 of his ''very closest friends.'' For many of the postwar years Mr. Capote traveled widely and lived abroad much of the time with Jack Dunphy, his companion of more than a quarter-century. He turned out short- story collections and nonfiction for Vogue, Mademoiselle, Esquire and The New Yorker, which first published ''The Muses Are Heard,'' a 1956 book chronicling a tour of the Soviet Union by a company of black Americans in ''Porgy and Bess.'' ''I conceived the whole adventure as a short comic 'nonfiction novel,' the first,'' Mr. Capote said. ''That book was an important event for me. While writing it, I realized I just might have found a solution to what had always been my greatest creative quandary. I wanted to produce a journalistic novel, something on a large scale that would have the credibility of fact, the immediacy of film, the depth and freedom of prose, and the precision of poetry.'' The result of Mr. Capote's discovery was ''In Cold Blood,'' which was almost universally praised. John Hersey called it ''a remarkable book,'' for example, but there were dissenters. Stanley Kauffmann, in The New Republic, sniped at ''In Cold Blood,'' saying ''this isn't writing, it's research'' - a sly borrowing from Mr. Capote's witty thumbnail critique, years earlier, of the rambling books of the late Beat Generation author Jack Kerouac: ''This isn't writing, it's typing.'' The critic Kenneth Tynan took Mr. Capote to task for being too strictly a reporter and not making an effort to have the killers' lives spared. Many readers were struck by Mr. Capote's verbatim quotations of long, involved conversations and incidents in his book. He explained that this came from ''a talent for mentally recording lengthy conversations, an ability I had worked to achieve while researching 'The Muses Are Heard,' for I devoutly believe that the taking of notes, much less the use of a tape recorder, creates artifice and distorts or even destroys any naturalness that might exist between the observer and the observed, the nervous hummingbird and its would-be captor.'' He said his trick was to rush away from an interview and immmediately write down everything he had been told. Mr. Capote was co-author of the movie ''Beat the Devil'' with John Huston and wrote the screenplay for a film of Henry James's ''The Innocents.'' Mr. Capote turned his second novel, ''The Grass Harp,'' into an unsuccessful Broadway play and, with Harold Arlen, wrote the 1954 musical, also unsuccessful, ''House of Flowers.'' Mr. Capote also adapted a number of his stories, including ''A Christmas Memory'' and ''The Thanksgiving Visitor,'' for television. Critics noted his deft handling of children as characters in his work, his ability to move from the real to the surreal, and his use of lush words and images. In 1963, the critic Mark Schorer wrote of Mr. Capote: ''Perhaps the single constant in his prose is style, and the emphasis he himself places upon the importance of style.''