But now many of those same readers are suffering Fifty Shades of withdrawal. They're feeling disappointed that the story ended, and left wanting more.
So you've read the trilogy, bought the merchandise, pondered which actor should play Christian Grey in the movie. So now what?
That's the question many customers who come into the Barnes and Noble store in North Fresno are asking.
"They're like 'oh, I wish I had another book like that', and we've got tons to recommend," Ashley Langford of Barnes and Noble said.
One of the most popular is "Bared To You" by Sylvia Day. The plot might sound familiar. Eva, a young woman making her way in New York City, and Gideon, the billionaire entrepreneur who pursues her. Both are emotionally damaged but their attraction and chemistry are explosive.
The author released the second title in the trilogy, "Reflected in You", earlier this month, and the third book, "Entwined with You," is set for release in early 2013.
But the mother and master of the erotica genre is Anne Rice. Inspired by the Fifty Shades phenomenon, her publisher re-released her trilogy based around the tale of sleeping beauty.
"Very beautifully written but very powerful like Fifty Shades, as far as what it talks about," Langford said.
If you're not quite ready to let go of the world of Fifty Shades of Grey, you can always throw a Fifty Shades party. Women everywhere are incorporating the theme with masks and grey neckties, a la Christian Grey.
Pinterest is full of ideas, like cakes, cupcakes, cookies and bookmark favors with "Christian-isms"
Others have gone even further, taking their Fifty Shades inspiration into the bedroom.
That's been good for business at Fresno's A U-Neek Boo-Teek.
"We've been getting a lot of couples coming in. Couples who've never purchased anything for, you know, the bedroom," Maricela Carrizosa of A U-Neek Boo-Teek said.
She says she's never seen a book inspire customers like Fifty Shades has. The shop had to stock up on items specifically mentioned in the book.
"They won't even have to tell me they're reading the book, they just pick out stuff. I'm like 'oh, are you reading Fifty Shades?' 'Oh how'd you know?' Because everyone's buying this!" Carrizosa said.
Maricela counts herself among the books' fans and like many of them she doesn't want the Fifty shades of fun to end.
"I'm like well, they're gonna make a movie, so I wanna keep the story in my head," Carrizosa said. "So I ended up just reading them again, so I'm on the second book again."