So, I don't know much about this series, but is this the kind of thing that have mass-market appeal as a film series? It seems geared heavily toward adult women; just how graphic is the story, and can it be given a PG-13 rating without being ruined?
The books have graphic NC-17 rated sex scenes. The movies need to be at least rated R to work.
Remember that these books are aimed at older female readers.
Even though some teens or kids read it, it doesn't mean it is aimed at them.