Thanks for digging it up! I missed this thread the first time.
Others have mentioned books that I still remember so fondly, The Chronicles of Narnia, A Wrinkle in Time (well, all, Madeline L'Engle really), Ann of Green Gables, and all Douglas Adams and Roald Dahl as well. All magical in my memory.
On the other hand, I remember being upset at The Velveteen Rabbit, Charlotte's Web and The Trumpet of the Swan. But as far as having lasting effect I'd have to go with Watership Down, which I read when I was 6 or 7. I think I was actually kind of traumatized by the violence. I remember being a little mad at my mom for giving it to me. I also have a vivid memory of staying up very late sitting in front of the heat vent in the winter to finish reading Roll of Thunder, Hear my Cry and crying, but I must have been a bit older then.