Several years ago, a colleague mentioned to Ann Brashares, then an editor at a New York publishing house, that she and some girlfriends had once shared a pair of pants during a summer.

Stefano Paltera, Associated Press Author Ann Brashares, left, who wrote the best-selling book "The Sisterhood of the Traveling Pants," poses for a portrait with cast members of the film, clockwise from bottom left, Amber Tamblyn, Alexis Bledel, Blake Lively and America Ferrera. Click photo for larger image. Related articles: Tamblyn and Lively enjoyed journey of 'Traveling' Post-Gazette movie review: Nice materials, poorly cut in 'The Sisterhood of the Traveling Pants', 6/1/05

Brashares thought that the story would make a great book. So the mother of three young children, who had never written a novel, sat down and wrote "The Sisterhood of the Traveling Pants."

Published in 2001, the book was a hit with teenage girls who loved the way Brashares used a pair of pants to represent the intense, unbreakable bond of friendship shared by four teens named Carmen, Lena, Bridget and Tibby.

"The Sisterhood of the Traveling Pants" climbed up the best-seller list and made Brashares an overnight literary sensation. Since then, Brashares, who has a philosophy degree from Barnard College in New York, has published two sequels, "The Second Summer of the Sisterhood,'' which was released in 2003, and the just-published "Girls in Pants: The Third Summer of the Sisterhood.''

Now, the series, which has sold more than 2 million copies, is getting an extra dose of attention with the release of a movie based on the first book.

"I think teen girls really like these books because the four protagonists are a genuinely diverse bunch of true friends," says Sophie Brookover, the senior children's and teen librarian at the Camden (N.J.) County Library.

"The issues each of the girls face -- romantic love, blended families, sibling rivalries, death of loved ones, and so on -- are true to life, and the characters handle them in realistic ways.

"Plus, with four protagonists, there's something to appeal to every reader in each of the titles,'' Brookover adds.

But there's one audience that doesn't seem drawn to the books -- boys. "I have not seen a single boy even pick up one of these books," Brookover says. "The books are uber-girly."

Kathie Fitch, a librarian at Rachel Carson Middle School in Herndon, Va., and a member of the Young Adult Library Services Association's Quick Picks for Reluctant Young Adult Readers committee, says students like the books "because they don't always end the way you want it to end, but they always end so you are positive about it."

The "sisterhood" of the four protagonists of the books actually begins before birth, when their mothers meet during an aerobics class for pregnant women. The girls (plus Bridget's twin brother, Perry) are born within a few weeks of each other, and their mothers form an instant support group.

The mothers' friendship dims as the children grow older, but the bond among the girls grows, despite their divergent personalities and backgrounds, and the fact that they go to different schools in the Bethesda, Md., area.

When the first book opens, the girls are 15 and about to spend their first summer apart. As they get ready to say goodbye, they decide to try on a pair of thrift store jeans that Carmen had purchased one day and then promptly forgot. Magically, the jeans somehow not only fit each of their very different bodies, but also accentuate just the right physical attributes for each girl.

The girls then decide to create the "Sisterhood of the Traveling Pants," complete with a set of 10 rules, including "You must never wash the Pants'' and "You must never let a boy take off the Pants (although you may take them off yourself in his presence)." The rules end with: "Remember: Pants = love. Love your pals. Love yourself."

As the girls quickly discover, the pants don't always bring good luck. But the pants do bring the girls back together again at the end of the summer, despite their varied adventures.

While Brashares doesn't sidestep controversial topics in her books, she has tried to write about them subtly enough that readers of different ages take away different things. For example, Bridget's sexual encounter in the first book is "alluded to, but it's not directly spoken about," Fitch says.

Brashares now is at work on a fourth (and likely final) book in the series. She also is working on her first novel for adults.

Meanwhile, she's grateful for the fact that her "Sisterhood" books have resonated so clearly with teen readers: "I sense that they have responded, more than anything else, to the unconditional love and loyalty the Sisterhood represents."