First, I find Eve Tushnet's point on The Giving Tree interesting, because my advisor has claimed that the book is a perfect example of what's disordered in a Christian notion of sacrifice.
Second, re: children's books. I am perfectly happy to be an adult, perhaps too much so: I'd much rather relive 25 (bad as that year was) than 15 or 10 or 5; I get to do what I love all the time. If you were to ask me what my favorite books were when I was a child, you'd get Killing Mr. Griffin, The Wind in the Willows (which I read rather late), and then a whole lot of nothing. There's much to be said for children reading, and reading in an indiscriminate manner: you learn the joy of a book in a way you can't when you're older. Having said that, I think I have, Wittgenstein-like, thrown down the ladder after surmounting it. Babar is a fine book, but Dante's Comedy is much finer, in every way. It's difficult to go back to the old valuation. Indeed, I only ever do so vicariously, asking what book my nephew would like most to read.
Here's the place where I drop T.S. Eliot in support of my position:
I may be generalizing my own history unwarrantably, or on the other hand I may be uttering what is already a commonplace among teachers and psychologists, when I put forward the conjecture that the majority of children, up to say twelve or fourteen, are capable of a certain enjoyment of poetry... Recognizing the frequent deceptions of memory, I seem to remember that my early liking for the sort of verse that small boys do like vanished at about the age of twelve, leaving me for a couple of years with no interest in poetry at all. I can recall clearly enough the moment when, at the age of fourteen or so, I happened to pick up a copy of Fitzgerald's Omar which was lying about, and the almost overwhelming introduction to a new world of feeling which this poem was the occasion of giving me. It was like a sudden conversion; the world appeared anew, painted with bright, delicious and painful colors.
Quoted, as ever, from The Use of Poetry and the Use of Criticism, which is itself one of the very formative books in my experience (I first read it in 11th grade, I think, which means it's been with me for over ten years now). Not to discount Helen's experience, which does not seem to be centered on books in quite the same way mine is. I'd argue that everyone must undergo something like Eliot's conversion moment. The works change: "Horatius at the Bridge" is, as Eliot implies, as appropriate for boys as "lead soldiers and pea shooters;" the unspoken implication is that "Horatius" is for the adult as the pea-shooter: less fitting because in a different context.
I don't mean to be a kill-joy about children's literature, I just think there are great and real pleasures that come with age.