Am I the last to know?

So I was finally convinced to read the first Fifty Shades of Grey book, not knowing by the way that the books are rather raunchy.  As I was reading it, I kept thinking that the book was pretty much Twilight with sex instead of vampires.  So am I really the last person on the planet to know that the Fifty Shades trilogy was originally an online Twilight fan-fic?