But it's doing more than selling books. It might be saving relationships.
The romance thriller is like Viagra for women, no prescription needed.
"There's a lot of sex in the books. It's all about sex," laughed reader Penny Bradley. "But it's also a love story."
"It was the first paragraph. It got me hooked right away," said reader Myung Neumann.
The friends talk about the book, quote the book and promote the book. But not all women are fessing up to what they're reading.
Dubbed "mommy porn," the trilogy is made up of novels 50 Shade of Grey, 50 Shades Darker and 50 Shades Freed. They took off first as e-books people could read in private.
But they now hold the top three spots on the New York Times bestseller list for both e-books and trade paperbacks.
"It was just good. I couldn't keep my hands off of it. You had a bite of something good and you want more and more and more. That's how I feel right now," described Neumann.
And it's not just the story women want more of. They want more of their men, and they're not shy to admit it.
"Men think about sex every 7 minutes, so why can't women talk about it, read about it, what's the difference?" said Neumann. "It's like if you say 'sex,' it's a big taboo and it isn't. It's part of life. It's part of a relationship."
That's the sort of statement counselor and life coach Peggie Dickens loves to hear.
"Now we're starting to tell each other. How fun. How fun," said Dickens.
She praises the books for helping women find that lost libido. No wonder sex therapists across the country recommend the book to their clients.
"All of a sudden, whew! This is stuff that we don't really talk about. But then when we read it our bodies react," Dickens said. "And I think that for people who are not having their bodies react very often, this is fantastic."
Penny Bradley whipped through all three books, and now her boyfriend is reading them too. And they're not just reading.
"It's renewed, it's fresh," Bradley said. "There's a spark there that has been, I don't want to say it was dead, but the light was out. It feels good. We're having fun with each other."
While the steamy scenes have couples back in the bedroom, women want to experience another part of the book too: the places.
The story is set in Seattle, with the billionaire bachelor leading man living in the penthouse of the Escala. Several times a week, book fans wander into the lobby asking for a look around.
"It's a private building and we've got so many homeowners that have moved in, so it's by appointment only," said Kathy Crotts of the Escala. "So they don't have that opportunity to access the common areas and see the different models."
Tours are for serious buyers. But the Escala made an exception for our cameras, letting us check out the home just a floor below the occupied penthouse. Like in the book, there is a wall of glass showcasing an endless view.
But much is, of course, fiction. There is no helicopter landing pad.
And readers will know what I mean when I say there are red accents, but no red room.
And the handsome, wealthy bachelor?
"That's an interesting question," Crotts laughed. "I think I'm going to fall back on the privacy of the homeowner and not answer that question!"
Some things are better left to the imagination.
And when a book can do that, it's no wonder women are reading it, talking about it, and recommending it.