My mom's rule for me--and I was a positively voracious reader as a kid--was that if I could pick it up, I could read it. She found that without interference from her, I generally either put down a book that was too mature for me or I ignored the parts that weren't right for me.
Granted, I wasn't a particularly highly sensitive GT kid. Sex and/or violence didn't really faze me like they do some kids. I read "Gone with the Wind" in 3rd grade and loved it. I read "Wifey" in 4th, I think, sex and all. But I loved Judy Blume, so reading her adult novel was pretty much a no-brainer for me.
I'm not saying that's the right tack to take for everyone (or even for anyone else), but I do think it worked pretty well for me. I think such material can just provide an opportunity for "teachable moments" about our family's values. I'm much more conservative in my approach to TV and movies than I am to books.
