C.S. Lewis was a most unlikely children's book author.

For one thing, Lewis had little experience of children until he married at the age of 58 and became a stepfather to his new wife's two young sons. Prior to that, his main knowledge of children came from the young evacuees who spent part of World War II in the house he shared with the mother and sister of a wartime buddy.

In addition, Lewis -- whose given name was Clive Staples, but who was known as Jack -- was a highly respected scholar. By 1950, he had become internationally famous for both his essays on medieval literature and his books on Christianity.

Yet his most enduring work may be a seven-volume children's fantasy series, set in the imaginary land of Narnia. The series, called "The Chronicles of Narnia," focuses on the battle between evildoers like the White Witch and the forces of good, led by a mighty lion named Aslan.

Since the first volume, "The Lion, the Witch and the Wardrobe," was published in 1950, the "Narnia" series has sold more than 95 million copies in 30 different languages. Beloved by generations of children, the books have inspired many other writers, including J.K. Rowling, whose "Harry Potter" series also will comprise seven volumes.

The books also have sparked controversy over their Christian themes. Lewis, who died in 1963 at the age of 64, freely acknowledged what he called the "hidden story" in his "Narnia" books, but he also said he worked hard to write the kinds of fantasy tales he so loved in his boyhood in Belfast, Ireland.

As a result, many children read the books purely for the pleasure of the stories, said Cynthia Richey, who recently served as president of the Association of Library Service to Children, the national organization of children's librarians.

"These are fairy tales in the grand tradition. There is wonder and magic, there is the classic battle between good and evil, and there is a satisfying resolution where good triumphs," said Richey, who is director of the Mt. Lebanon library. "The books are empowering to children, who believe that they, too, can thwart the Witch. And they like the idea that somewhere out there is a world where they can escape through something as simple as a wardrobe."

The "Narnia" books have remained steadily popular, selling about 1 million copies annually. Now, with the first full-length feature film, interest in Lewis' "Narnia" books has hit new highs.

Marketers are working hard to further rachet up "Narnia mania" by touting a variety of products tied to the release of the movie. But in literary and theological circles, there continues to be a debate as to why an eminent scholar like Lewis decided to write a children's book series. A.N. Wilson, author of "C.S. Lewis: A Biography," says that Lewis wrote the Narnia chronicles for "the child who was within himself."

David Downing, in his new book "Into the Wardrobe: C.S Lewis and the Narnia Chronicles," adds that writing for children allowed Lewis "to pour more of his whole self into his writing, including his love of wonder and enchantment, his affection for animals and homespun things, his shrewd observations about human nature, his vast reading, and his robust humor."

Lewis had said he began writing "The Lion, the Witch and the Wardrobe" with a "picture in my head ... of a faun carrying an umbrella and parcels in a snowy wood." He first had the vision at age 16; he was nearly 50 when he transformed it into the beginning of the book.

Another inspiration was the wardrobe in which Lewis and his older brother, Warren, used to play. The wardrobe now can be viewed at the Marion Wade Center at Wheaton College, Ill.

Christians have long praised the series as an enticing introduction to the basic ideas of faith. Lewis, who was an atheist until his conversion at age 32 (with a nudge from his devout Catholic friend, J.R.R. Tolkien), wanted to find a better way to teach religion to children.

"Sometimes fairy stories may say best what's to be said," Lewis once said.

One of the harshest and most widely read critics of the "Narnia" themes is author Philip Pullman, whose critically praised "His Dark Materials" fantasy trilogy is meant as an atheist answer to Lewis' series.

Tolkien felt that Lewis' "Narnia" books weren't particularly well thought out and were too derivative of other literature -- unlike his own "Rings" series, where he created his own fantasy world.

The "Narnia" books, Tolkien declared, "just won't do."

Millions of readers have decided that they'll do just fine.