"THERE NEVER WAS a simpler happier family until the coming of Peter Pan," wrote the author of that sinister classic that, even degraded as musical comedy, keeps its hold on the public after 75 years. There was indeed a real Darling family and Peter Pan was J.M. Barrie himself. He came as a lover and destroyer.

Arthur Llewelyn Davis and his wife Sylvia, born a du Maurier, were a beautiful, charming and somewhat impecunious couple. Their five sons, George, Jack, Peter, Michael and Nicholas, were born between 1894 and 1904. The playwright slipped into the household like Peter Pan, through the nursery, and made Arthur's and Sylvia's boys "my boys." It would be difficult, unless one belives that cancer can be brought on by choked-back chagrin and by grief, to maintain that Barrie killed off the parents, but within 10 years of their sons having become the passionate center of his life, Arthur and Sylvia were conveniently dead. How this strange relationship came about is told by Andrew Birkin in a remarkably skillful and moving account, based on letters, documents and reminiscences, that is as sympathetic to Barrie as to the Llewelyn Davies family.

Barrie had first laid eyes on the elder boys in Kensington Gardens; they were set apart by their good looks and fetching red velvet berets. Barrie was noticeable too. At 5 feet 3 inches, he was smaller than his companion, a St. Bernard dog, and his stories were bewitching. He began to go home with the boys, to continue his spell until bedtime. To Sylvia the disruption was a small price to pay for the attentions of a celebrated author, but to the boys' nurse and their father, a barrister who could only see his sons at bedtime, the nightly visits were an affliction.

Why a popular middle-aged playwright should have invested all his emotional resources in someone else's children is a mystery rooted in his own painful childhood: the early death of a favored older brother helped convince him that the best of life is soon outgrown and must be clung to by any means. One way was to die young; another was never to grow up, to remain forever his mother's precocious little boy, for whom the only acceptable human relations were between children and parents, especially mothers. Men and women as mature, sexual adults aroused his fear and hostility.

His own marriage to a pretty actress was loveless and sexless, and ended in her leaving him. His contempt for marrige is expressed repeatedly in the plays that made him rich and famous. Why should audiences have lapped up the bittersweet mixture of sentimentality and sadism that was his trademark ("whimsy" they called it)" Peter Pan combines sweet escape from the adult world and revenge upon it with the least disguise.

That play was the literary capital he made out of his love affair with the Davies boys -- for he wasted nothing, habitually managing life so to make it produce literary copy. He played with children as their equal and fed their boundless young egos with flattery that would have choked an adult. He never retreated into grown-upness. If a boy hurt him, he hurt back. He knew the glamour of destruction and violence and would of "smashing" a child; he would give little boys matchboxes to play with; real knives and arrows figured in the game of boy castaways. His ultimate purpose was to establish possession. In a thinly disguised fiction he wrote of a scheme "relentlessly pursued -- to burrow under [Sylvia's] influence with the boy [George], expose her to him in all her vagaries, take him utterly from her, and make him mine." Peter Davies, the middle son (who, shell-shocked during World War I, eventually committed suicide at 62), later wrote, "I doubt if he brought out or even recognized (or wanted to) the true characteristics of anyone he made much of; he was such a fantasy-weaver that they ended by either playing up to him or clearing out. When he was strongly attracted to people, he wanted at once to own them and to be dominated by them, whatever their sex." His ownership of George involved strange moments. Writing of an overnight visit from the little boy, he sounds like Humbert Humbert: As he undressed him on his knee, "I remained wonderfully calm until I came somewhat too suddenly to his little braces, which agitated me profoundly. I cannot proceed in public with the disrobing."

He was a disruptive, subversive force in the Davies household, subtly undermining authority; when the boys were ready for school, their headmaster figured as a villain in the compelling fantasy life he spun about them. Worse perhaps was the way he whipped young fancies up to fever pitch. His mastery of the gifted Michael's imagination exacerbated the little boy's nightmares and sleepwalking. "There was a horror looking for him in his childhood," Barrie wrote, without irony. He made the afterlife of the dead boys of Kensington Gardens, among pirates and Indians, sound so thrilling to George that he exclaimed the words later put in Peter Pan's mouth: "To die will be an awfully big adventure."

From the first appearance at Christmas 1904, and every Christmas thereafter, Peter Pan was a smash -- though there were dissenters like the man heard exclaiming, "Oh, for an hour with Herod!" Writing about the play 25 years later, in a dedication to the boys, Barrie said, "I clutch my brows in vain to remember it was a last desperate throw to retain the five of you for a little longer, or merely a cold decision to turn you into bread and butter." It was both, of course, and a revelation of his own inner life.

Arthur, so much admired by friends for his simplicity and patience, made no comment on his portrait as the repulsive Mr. Darling, and probably did not know how Barrie referred in another fiction to his "trumpery love" for Sylvia. Apart from losing one of two copies of a book Barrie had concocted out of the boy-castaway game, he endured the invasion of his family without comment. In 1906 a drastic operation for sarcoma mutilated his face and speech. Faced with death, he surrendered to Barrie who paid the bills and sat at his bedside making notes for stories about dying men. Arthur dying was finally someone Barrie could care for.

Two years after Arthur's death, the lovely grieving Sylvia began to ail. An inoperable cancer, debilitating but not painful, was found "near her heart." If after her death in 1910 there was any doubt who "owned" the boys, Barrie dismissed it by altering her will to indicate she wanted him as guardian. "Mrs. Darling was not dead and forgotten," he wrote, while he distracted her sons from mourning with expensive fishing gear, the beginning of a boundless flow of amusements, treats and luxuries that dismayed their late parents' friends. Later Peter expressed regret that he and his brothers had had so much light entertainment and so little real culture.

Dreading his loss of possession as they grew up, Barrie worked on their feelings. "the rebuffs I got from all of you!" he wrote. "They were especially crushing in those early days when one by one you came out of your belief in fairies and lowered on me as a deceiver." Remembering a grateful smile, he plaintively quavered, "I keep the smile with the few other broken fragments of immortality that have come my way." The boys swallowed this stuff and remained loyal, though school friends viewed their guardian with "utmost dislike"; a girl friend remembered, "There was something very sinister about him, rather shivery."

When George when to France as an officer in 1914, Barrie deluged him with anxious letters, wishing George was a girl so that he could say what he felt without impropriety yearning that they might grow "closer and closer to each other." The handsome, good-natured eldest brother was killed in March, 1915. It says something about Barrie's hold on them that the brothers pitied him even more than they grieved for their own loss.

But he still had his adored Michael. The 2000 letters he and Barrie exchanged during his years at Eton and Oxford were later burned by Peter. They were "too much," even for someone used to Barrie's shameless emotional manipulation. To the youngest, Nico, he wrote, "I would really rather you grow down instead of up," but all were groping toward their separate lives. When Michael ventured a wish to study art in Paris, Barrie persuaded him to remain at Oxford. Dora Carrington noticed the young man's unhappiness and told Lytton Strachey, "Perhaps that is just the gloom of finding Barrie one's keeper for life." Yet Michael escaped the cage. In May 1921 he and a friend drowned together in what was probably a homosexual suicide pact.

Peter Davies observed that Barrie's "connection with our family brought [him] so much more sorrow that happiness." Yet it is impossible to read this terrible and fascinating story without feeling that it was the other way around -- though Birkin is careful not to express opinions or judgments. The photographs of these beautiful, doomed people thickly scattered through the text, many taken by Barrie, make the story the more deeply poignant.