“Anything becomes interesting,” said Gustave Flaubert, “if you look at it long enough.”

It could have been Truman Capote’s motto. He spent six years looking at the murder, in November 1959, of four members of the Clutter family in Holcomb, Kansas, by two passing hoodlums, Perry Smith and Dick Hickock. Finally, as Smith and Hickock were executed in 1965, he published his account of the whole story, In Cold Blood. It sold, and still sells, millions. But Holcomb also seems to have passed a death sentence on Capote. His next book — the unfinished novel Answered Prayers — was minor in comparison and alienated all his New York friends with its lacerating description of their lives. He produced nothing further of substance. He died in 1984 of pills and alcohol. Possibly it was suicide.

Capote was short — 5ft 3in — and spoke in a strange, high-pitched Southern accent. He was a wildly camp gay who effortlessly held whole parties in thrall with his anecdotal brilliance and cool outrageousness. I have always remembered one story about him, which I hope is true. At the height of his fame, a lady spotted him in a restaurant, rushed over and asked him to autograph her breast. Capote did so. Her husband, incensed, strode over, took out his penis and suggested Capote might like to autograph that too.

“Well,” responded Capote, “perhaps I could initial it...”

Such a man invites myth. As with many, many modern literary outsiders — Wilde, Salinger, Kerouac, Burroughs, Pirsig — the mystery and meaning of the life seem to tower over the work. In Capote’s case, the myth pivots on the strange, central contrast between the camp, New York party animal, the author of Breakfast at Tiffany’s, and the macabre austerity of that Kansas killing in the midst of the kind of flat, empty landscape that makes coastal dwellers shudder.

“The village of Holcomb,” runs the famous first sentence of In Cold Blood, “stands on the high wheat plains of western Kansas, a lonesome area that other Kansans call ‘out there’.” This location is doubly remote. Kansas, to Capote’s prime readership, is already “out there”, but Holcomb is exiled yet further into the emptiness. And then there is the final “out there”, the ultimate badlands, the minds of Smith and Hickock: drifters, loners, killers.

Bennett Miller’s film Capote — up for five Oscars including best film, best director and best actor for Philip Seymour Hoffman — hinges on this contrast. It tells the story of the writing of In Cold Blood, showing Capote at New York parties and in Kansas, exploring the bleak badlands of the killers’ minds. It shows him as morally dubious — he wants the men to die so he can finish his book, but he pretends otherwise — and intellectually cold. But, equally, it is an admiring film. The sheer effort and focus of Capote at work is overpowering, and the greatness of the finished book is never questioned.

Oddly, this film seems to have temporarily buried another on the same subject. Douglas McGrath’s Infamous, with Toby Jones as Capote and Sandra Bullock as his friend Harper Lee, has been completed but has, as yet, no release date. Plainly Capote is on the agenda. Why? Partly, I suspect, because the mythologising impulse has exhausted the 1960s and has taken one further step backwards in time. Dylan, for example, has been done and so we get Johnny Cash in Walk the Line. Similarly, we have had Hunter S Thompson, so perhaps now it’s time for Jack Kerouac — and, indeed, Walter Salles’s film On the Road is due out next year. (Capote, incidentally, said Kerouac’s work was typing, not writing; to which one critic responded that Capote’s was not writing but research.) The post-war era has begun to take on a distinct, self-contained reality, perhaps because it’s over; a series of apparently clear plot lines has begun to emerge and, in our imaginations, we are trying to make sense of them.

But Capote is not a line, he is a node, a crossing point. An outsider from the first, he arrived in New York from the South with his mother and stepfather in 1933. He was never anything but obviously gay and seldom less than brilliant.

A school IQ test is said to have registered a figure of 215, which is highly unlikely and probably impossible. His education was interrupted and incomplete, but, in later interviews, his list of literary heroes is prodigiously long and his critical awareness acute. Flaubert comes up again and again.

In the 1940s, he made his way to The New Yorker magazine and started producing admired fiction, which, with Breakfast at Tiffany’s in 1958 (filmed with Audrey Hepburn in 1961), also became popular fiction. He was already famous when he boarded the train to Kansas, having spotted the story of the Clutter killings in The New York Times.

In Cold Blood was a sensation, selling millions but also earning Capote fabulous literary acclaim. Norman Mailer called him “the most perfect writer of my generation” and went on to write his own In Cold Blood in the form of The Executioner’s Song (1979), about the execution of Gary Gilmore in another “out there” remote and alien American landscape, Utah. Capote didn’t return the compliment, regarding Mailer’s use of researchers to do the legwork with disdain. The reviews of In Cold Blood were largely raves and generally accepting of Capote’s own analysis that this “nonfiction novel” represented a major literary breakthrough, comparable to the publication of Joyce’s Ulysses.

“The motivating factor in my choice of material,” he said in an interview with George Plimpton, “that is, choosing to write a true account of an actual murder case, was altogether literary. The decision was based upon a theory I’ve harboured since I first began to write professionally, which is well over 20 years ago. It seemed to me that journalism, reportage, could be forced to yield a serious new art form: the ‘nonfiction novel’, as I thought of it.”