What is the most serious book that you have enjoyed?

Question:

What is the most serious book that you have enjoyed?

Fiction/nonfiction?
Any Genre?

More than one suggestions are welcome.

Best Answer - Chosen by Asker: "A Child Called It"
"Where the Red Fern Grows"
"Puddn'head Wilson" by Mark Twain
"China Boy" by Gus Lee
"The Kitchen God's Wife" by Amy Tan