Thats the main problem! the very fact that this is the first exposure millions of readers have to a genre thats been around 200 years or more, and the book is pretty much one of the worst, and that's what annoys me the most. Why weren't all these women already reading this genre? because before now it was seen as taboo and didn't have an Apple level marketing campaign making it "ok" to read it.
It wasn't written for the Twilight crowd, it was written for over 18's and many stores won't sell it to anyone younger. Twilight, Divergent etc are sold in the childrens section of books stores and marketed for mainly mid teens. 50 Shades is an erotic novel and would normally be placed in the section of the store most feel embarrassed browsing.