I remember reading Pippi in the South Seas, by Astrid Lindgren, when I was eight, laughing out loud, and having the epiphany that black marks on a white page had just made something amazing happen inside me.
Charlotte's Web, by E. B. White had an ending so bittersweet, arousing such complicated emotions in my nine-year-old self, that I felt I had grown up a little bit for having read it.