I tend to read all the books I'm assigned in school before we analyse them so I can keep my love for them.
I would be hard put to name any single book that has affected me in some way. In my opinion, most books (good books, anyway) will have some wise words of wisdom, or some thought provoking idea. I often reach a realisation by reading a book, simple or not.
Remembrance by Theresa Breslin (I think) made me think about how people forget about war by and by. Actually, I think a lot of my conclusions come from thoughts that were inspired by a book but not actually included in a book.
Lord of the Flies seriously distressed me though. Ever since I read that book, I have had a pessimism about humanity implanted in me.
I liked
The Chronicles of Narnia - I could see where the symbolism came in and the books were good reads besides.
The Last Battle was really good. I loved the ending and the ideas it presented. And other books like that were
His Dark Materials and the
Lord of the Rings.