Part of the reason I am such an avid reader today is because my parents had around 8 bookcases full of good, classic, adult books. There was no objection to my reading most of them at a young age (I started really devouring books when I was around 9 or so) because they were "clean", so to speak. There certainly wasn't much, if any, hardcore profanity, and any sexual subjects were handled in a "not in your face" way. When my daughter was younger (she's 18 now), I would have loved to have allowed her the same freedom with my books that I had as a child, but there was no way in hades I could do that with most current books marketed for adults.
I realize I'm in the minority here, but just some food for thought.
