Lolita was 12 when Vladimir Nabokov brought her to life as the obsession of the man who would become her stepfather, a middle-aged man who calls her "light of my life, fire of my loins. My sin. My soul. . . . Lo. Lee. Ta."

After three generations, readers remain relentlessly drawn to Nabokov's opening lines -- more poetry than prose. They remain equally repelled by Humbert Humbert, a child molester who essentially holds his stepdaughter captive; he is as despicable today as he was in 1955.

"Lolita," a deceptively thin volume, has sold 50 million copies. Vintage Books already has sold all 50,000 copies of a 50th-anniversary edition it released this month.

A close-up of a young woman's mouth replaces the previous cover photograph, a black-and-white photo of a girl's legs, in ankle socks and saddle shoes.

"Lolita" and "nymphet" -- another word Nabokov coined -- have worked their way into the lexicon. Two movie versions, first by Stanley Kubrick in 1962 starring James Mason and later by Adrian Lyne in 1997 starring Jeremy Irons, have coaxed millions into theaters. More recently, Iranian author Azar Nafisi penned her own contemporary bestseller, "Reading Lolita in Tehran: A Memoir in Books," inspired in part by Nabokov, and the "Gothic Lolita" is all the rage among teenage fans of Japanese anime.

How is it that a pedophile protagonist remains sympathetic enough to draw audiences? Why does this backward fairy tale -- Prince Charming as a monster -- endure?

Literary critics say the explanation is simple: art.

"No one respected language more than Nabokov," said Stephen Parker, a student of the author's at Cornell University in the late 1950s who founded the Nabokov Society at the University of Kansas. "You don't read it for his ideas, you read it for his presentation."

Parker says the Russian-born Nabokov, who made his fortune with "Lolita," was less concerned about teaching a lesson in morality than he was in creating a long-lasting work of art.

"Get beyond the story, the entertainment, and get into what was more important," Parker said. "That's the case with 'Lolita.' The reason it's such a great work is because it has such great depth. . . . It's endlessly revealing. And that's what the finest fiction should be."

Nabokov's son, Dmitri, 71, who lives in Montreux, Switzerland, and for years served as his father's translator, exchanged e-mail with the Associated Press about "Lolita."

"A work of art, not its subject, remains eternally powerful," he said. "The book exists on several levels, and in it there coexist many themes: poetry, humor, tragedy, love. Perhaps its most moving quality is that it is not black-and-white."

While Nabokov began writing "Lolita" in the late 1940s, he completed much of it at his Ithaca, N.Y., home while teaching at Cornell. It's the story of Humbert, a pedophile who is obsessed with his young stepdaughter and essentially kidnaps her, traveling across the country and holding her sexually captive. She eventually leaves him for another pedophile, and Humbert goes to prison for murder.

Nabokov was a methodical researcher, filling hundreds of index cards with pencil-written notes and drawings: statistics on the height and weight of school-age girls, popular jukebox tunes, details from a gun catalogue about the murder weapon Humbert uses to kill Lolita's lover. He even spent hours on school buses, observing teen speech, Parker says.

He knew it would be controversial; Nabokov called the novel a "time-bomb" and hid the manuscript, writing notes to remind himself where he had secreted the pages. At the time, he planned to publish the novel using a pseudonym, to ensure it wouldn't sully Cornell's reputation.

In December 1953, Nabokov delivered the 450-page manuscript to Viking Press in New York. He was told it was brilliant but that any publisher who accepted it risked being fined or jailed. Rejections from five U.S. publishers followed.

Then "Lolita" made its way to Paris, to Maurice Girodias, founder and owner of Olympia Press. Girodias's father had published Henry Miller's "Tropic of Cancer" and "Tropic of Capricorn" in the 1930s. Following in his father's footsteps and eager to make money, Girodias published English-language pornography that had been censored elsewhere.

Ignorant of Girodias's sketchy reputation -- Nabokov says he "knew nothing about the obscene novelettes" he was producing -- the author signed a contract and even agreed to publish it under his own name. "Lolita" came out in Paris in September 1955.

Almost no one took notice at first; it was neither reviewed nor advertised until novelist Graham Greene named it one of the three best books of 1955 in the Christmas issue of London's Sunday Times.

By 1956, the book was banned in France. (That ban was overturned two years later.) "Lolita" was published in the United States in August 1958 and immediately drew rave reviews from writers Dorothy Parker, William Styron and others. It became the first book since "Gone With the Wind" to sell 100,000 copies in its first three weeks. Movie rights were quickly snatched up by Kubrick.

The book got "extraordinary publicity" and was "an enormous bestseller" that made Nabokov's colleagues at Cornell immensely envious, says Stephen Parker, who teaches Slavic languages and literature at University of Kansas.

The novel's quality was difficult to dispute. Students lined up at Nabokov's office to get their copies autographed.

Parker says he admires Nabokov's "exquisite" use of the English language, which is especially remarkable since Russian was his native tongue. Dmitri Nabokov said his father "could even endow a shopping list with an original rhyme or twist."

Far from being banned from publication in the United States as Nabokov had feared, "Lolita" earned the author a fortune. He quit teaching, moved to Switzerland and returned to writing full time, publishing several other novels and short stories, although none as popular as "Lolita."

He later told his son that he'd accomplished all he ever wanted to as a writer. Nabokov died in 1977.

Nafisi, author of "Reading Lolita in Tehran," sounds breathless when she says that "Lolita" is one of the world's great works of art because it reaches the emotions so many people hold deep inside. She has lost count of how many times she's read it, but each time, she uncovers something new. In 1995, when she read the book with seven of her students in Tehran -- an all-women book group, illegal under Iran's Islamic regime -- she said it reawakened her senses.

"We lived in a country that had no respect for art, for literature," she said. "We really appreciated the language of it. We became alive again."

Nafisi's experience became the anchor for her best-selling memoir.

"What frightens or disturbs us in 'Lolita' has something to do with us," she says. "It opens our eyes to ourselves and our worlds. Everyone should read it for the pure joy."

Vladimir Nabokov, in a 1976 photo, published "Lolita" in 1955. Since then, it has sold 50 million copies and all of its 50th anniversary editions.