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Like Mary Poppins, the character she created, P. L. Travers did not believe in explaining. She did, however, believe in self-mythologizing, leaving those intent on biographical criticism so confused in her wake that even her obituaries had the facts wrong (according to Valerie Lawson, author of "Out of the Sky She Came," the definitive Travers biography).

PLT, as she was sometimes called, did not even take credit for "creating" Poppins. Instead, she insisted, the nanny with the upturned nose just came to her one day, much as she blows in on the East Wind in the opening chapter of "Mary Poppins" (1934). But whether Travers created the "Practically Perfect" Poppins — while convalescing from pleurisy in her Sussex, England, cottage — or merely channeled her, the world is in her debt.

Despite the obfuscation, many facts of the author's life are indisputable. Pamela Lyndon Travers, as she was fully known in her adult life, was born Helen Lyndon Goff in Maryborough, Queensland, Australia, in 1899 (although the dust jacket of one of her own books claims it was 1906). She took her professional name — Travers was her father's first name — during a brief stint as a dancer and actor. She left Australia permanently in 1924, after which she lived principally in England, but with periods in Ireland and the U.S. (for a time with the Navajo).

PLT's early life was fairly idyllic, until her father died when she was only seven. The eldest of three girls, she was remarkably imaginative, given to pretending she was a hen, spending hours brooding on an imaginary nest of eggs. She loved reading and ingested the Brothers Grimm (especially the gory bits). For a time in her childhood she thought "grim" was another word for story. "Tell me a grim," she would say. The child fantasist grew up to become quite self-sufficient, very much an "independent woman," and years ahead of her time. To quote from Caitlin Flanagan's 2005 New Yorker piece, "Travers was a woman who never married, wore trousers when she felt like it . . . [and as] she approached forty, she decided that she wanted a child. . . . [So she adopted] an infant, one of a pair of twins, and raised him as a single mother."

After leaving Australia, where she supported herself as a journalist, Travers matured into a poet, critic, and essayist, and "a serious writer" of fiction and nonfiction books. Her circle of acquaintances included William Butler Yeats and T. S. Eliot, and her personal interests ran to mythology and mysticism (she was a longtime disciple of guru G. I. Gurdjieff). PLT reduced her alias to its initials to disguise her gender, hoping to escape the dismissive stereotype of the lightweight authoress.

The great success of "Mary Poppins" was immediately followed by "Mary Poppins Comes Back," in 1935. "Mary Poppins Opens the Door" appeared in 1944, followed by "Mary Poppins in the Park," in 1952. These four books — collections of stories with recurring characters rather than novels — are the core of the nanny's canon. The books have long been published in the U.S. by Harcourt Trade Publishing. The last of the Poppins tales, "Mary Poppins and the House Next Door," appeared in 1989.

Travers may not seem the kind of individual to have been wooed by Walt Disney, but pursue her he did, or at least the film rights to "Mary Poppins," a favorite of his own daughters. It took Disney 20 years to convince a strong-willed, proprietary, and altogether perfectionist Travers to approve a script and put her signature on the dotted line, which cost Disney five percent of the "Mary Poppins" gross (adjusted for inflation, the movie ranks as No. 23 on the list of all-time box-office earners).

It took legendary theatrical producer Cameron Mackintosh nearly as long to wrangle the stage rights. By the time he knew her, he says, "she was a frail old lady. But you could see that she had a steel rod going down her spine. ... She asked me lots of questions about her characters and what kind of musical I wanted to do on stage. When I started to dig for information I felt very like Michael and Jane Banks waiting to be told, 'You'll do.'"

Ultimately, Mackintosh did acquire the theatrical rights and met with Thomas Schumacher, president of Disney Theatrical Productions, to talk about the possibility of a joint production. Mackintosh gave Schumacher the treatment he had worked up for the stage musical. Schumacher gave Mackintosh an armful of documents from the Disney vault. "It was amazing," remembers Schumacher, "that Cameron had focused on many of the characters and episodes from the books that Travers wanted to include in the 'Mary Poppins' film sequel that was never made."

As is frequently the case with people who do not like to talk about their personal lives, that of P. L. Travers seems unusually freighted with frustration and conflict — especially in her relationships, both requited and not. Even her 50-year collaboration with illustrator Mary Shepard — herself the daughter of Ernest H. Shepard, who first drew "Winnie the Pooh" — was not always placid. Nonetheless, countless details from PLT's life found their way into her books.

After her father's death, Travers found herself living with her Great Aunt Helen (known as Aunt Ellie), for whom PLT was named. Ellie was an irascible and sometimes bitter spinster, described as variously peremptory and humane, given to sniffing disapprovingly and to quoting every bromide in the book of child rearing. She seems clearly to be, at least in part, the life model for "Mary Poppins." Not coincidentally, she made a habit of carrying a carpetbag. Physically, Mary Poppins is described as resembling a Dutch doll that was one of PLT's playthings as a girl.

Travers assigned her own father's occupation, bank manager, to Mary Poppins's employer, George Banks, along with Mr. Goff's money troubles. Two of the Banks children, Lawson points out in her book, are named after two of PLT's relatives in Australia. Even the Royal Doulton bowl that figures so prominently in "Bad Wednesday" from "Mary Poppins Comes Back" was an artifact from PLT's childhood. And her childhood nurse sported an umbrella with a carved parrot head for a handle.

That Mary Poppins is so widely considered a loving caregiver is one of the central mysteries of the books. Jane and Michael Banks are simultaneously devoted to her and terrified of displeasing her. Far from rosy-cheeked and flirtatious, as she seems from the film, the literary Poppins is described as strict, stern, remote, and rigid — and she can stop a child in its muddy tracks with her blue-eyed glare.

She is also given to shocking, and hilarious, turns of phrase. "I have the patience of a boa constrictor," she sniffs to Jane and Michael one day.

Aside from the frequent dreamlike adventures that take her charges out of the ordinary world, the Poppins program of parenting is not the kind of rearing you would expect children to enjoy — not today; not in Depression-era London, when the books are set; not in 1910, the period of the film. What is unique about Mary Poppins is her ability to impose order to the chaotic Banks household and a modicum of peaceful normalcy (between episodes of sorcery). Is Mary a magical fairy godmother, a disapproving authority figure, or a satisfying bit of both? Certainly she inspires fearful trepidation as well as awed admiration.

That generations of readers have loved Mary Poppins, and grieved at her successive departures from 17 Cherry Tree Lane, may be the biggest mystery of the conjuring nanny's hold on our collective hearts. Maybe it is the unexpected complexity that makes us cherish both Poppins and Travers. They don't offer us an easy life, just a fascinating one. If their enchanted rose gardens come with thorns, the flowers bloom in colors we have never before seen.

Perhaps Julie Andrews described Travers best: "I liked her," the Oscar-winning Mary Poppins has said. "She was an eccentric and rather tough old girl but a good-hearted one, I felt." Pamela Travers died in 1996, four months short of her 97th birthday.

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Michael Lassell is the author of "Elton John & Tim Rice's Aida: The Making of the Broadway Musical," "Tarzan: The Broadway Adventure" and, with Brian Sibley, the forthcoming book on bringing Mary Poppins to the stage (all from Disney Editions).