I've been really interested in the idea of "age-appropriate" books since I read a hilarious-to-me review from a mother who had read The Dark is Rising to her five-year-old (and, even though she didn't think it was good, recommended it for ages 6-9) a year or so ago. I don't have any children, but I have nieces who have been reading on their own for several years now, and I laugh at myself for sometimes being uneasy with them reading the kinds of things I read when I was their age. (Well, the oldest one is nine, so I'm projecting into the future a couple of years, maybe.)
Conversations about what books are and aren't appropriate for kids at particular ages seem to come up a lot on blogs and in the journals, so I take it a lot of people share my interest.
It occurs to me that I have stricter standards for what kids might see in movies than what they might find in books, and I'm comfortable with that. I think kids can roll over content they're not ready for in books much more easily.
I posted a while ago about a censorship article in School Library Journal; Justine Larbalestier wrote a terrific response to it, and many of the comments on her post are excellent. I especially recommend scrolling down to the two comments by "Lesley".
Since Justine, and others, have already written many of the things I might say, I'm going to ask a question instead. Is this really such an important topic? Did anyone here read anything during childhood that seriously upset/bothered/changed you, or made you lose your innocence too soon, because of content that someone might say was inappropriate for the age you were when you read it? (So, I'm not talking about things like the picture of raining gorgonzola cheese in Cloudy With a Chance of Meatballs; that's disturbing, all right, maybe nightmare inducing, but I don't think anyone could call it age-inappropriate.)
I'll be writing a post soon about my experience reading Gone With the Wind at age 11, but I'm still trying to think of any other examples. I can remember a couple of scary books, but I'm not concerned about my response to them. Mostly, I can think of books with possibly age-inappropriate content that I didn't understand until I was quite a bit older (like A House Like a Lotus, Madeleine L'Engle).
The only book I can think of that I really wish I'd never read, because it was too disturbing, was Apt Pupil by Stephen King (I know, it's really a novella or whatever), but I was 21 when I read THAT.
(I hope it's clear that it's totally okay if people do have examples to share--I hope you do, because that makes conversation more interesting.)