CLEVELAND, Ohio -- Fifty Shades of Controversy.
It's been called everything from "mommy porn" to "poorly written," but the hugely successful trilogy by E. L. James is something else: a bestseller.
The sizzling series and first installment, "Fifty Shades of Grey" is now the fastest selling book of all time.
Millions of copies are flying off store shelves and being downloaded by women of all ages from around the world.
But the fastest growing group of readers are teenage girls, and that has some parents concerned.
"I was a bit uncomfortable when I found out she was reading it," admitted Kathy Lehmann.
Her 18-year-old daughter, Taylor, recently brought home the series.
"I said, 'Beware,' "said Lehmann. "I mean, she's 18. If she doesn't read it at home, she's going to read it somewhere else."
Lehmann's daughter isn't alone. She and all of her friends who just graduated high school this past year have poured over the provocative pages.
"I know so many girls at school reading it," said Taylor Lehmann, 18.
"Actually, a lot of people at school are reading it," added Elizabeth Williams, 17.
The storyline is at times amusing, and sometimes mysterious, but at its core ... hardcore, it's very erotic.
In the racy series, worldly billionaire Christian Grey seduces and falls in love with an innocent recent college grad named Anastasia Steele.
The relationship evolves into "hearts and flower," but begins with BDSM: Bondage, Discipline, Sadism, Masochism.
Readers are introduced to terms like dominant, submissive and hard limits.
There's also spanking, whips, handcuffs and other methods of pain.
"I definitely didn't know half of the stuff in the book," said Taylor.
Still, the teens are huge fans of the "Fifty Shades" trilogy. And they've heard of girls as young as 14 reading the books.
"Some of my teachers got really upset that I was reading it in study hall," said Elizabeth.
The book's subject matter is so controversial that some libraries have banned it from their collections.
Some doctors say it's saved failing marriages, so much so they're expecting a baby boom next year, and the sex toy industry has seen a spike in sales related to items mentioned in the book.
The first book in the trilogy sold one million print copies in 11 weeks and combined sales of the book are over 20 million globally.
"I think a lot of its popularity is because it has explicit sexual scenes," said Dr. Lori Stevic-Rust.
The board certified psychologist learned of the books when her own teenage daughter brought it home.
She says it sparked a lot of conversation about what's appropriate and what's not.
"She spontaneously started having a conversation about, 'I'm reading this book, and it's a little disturbing,' " said Dr. Stevic-Rust.
Some of the concepts that might be too mature for girls under age 17 are scenes describing "signing an obedience sex contract," "the Red Room of Pain," and "stalking."
There is also the idea that a person can "change" or "heal" someone's broken past.
Dr. Stevic-Rust says although those topics are unnerving, they can also be used as an effective teaching tool.
"I think that's the advantage of it, is to really talk about those boundaries, and what we really can and can't do in terms of changing somebody," Stevic Rust said.
There are also several positive messages in the books like seeking counseling for problems, having safe sex and remaining anti-drugs.
Those points all seemed to resonate with the teens, but in the end, they say it was the simple boy meets girl love story that kept them engaged.
"It's not like, 'Oh, I read this and now I'm going to do all of this stuff,' " said Taylor.
"I really just liked the storyline," said Brittan Mariage. "It sounds cliché, but I really did just like the background to the story."