First of all, my favorite book, The Sea Wolf by Jack London, my favorite book of all time. It was about evolution vs. religion but also about life. It is very brutal, yet beautifully done. Brutality and manliness always get me.
Watership Down is the second one, a book I read every Easter without fail. It never grows old.
Death in the Afternoon by Ernest Hemingway- a manual about bullfighting, but also essays on war, death, very heavy stuff.
The Phantom Tollbooth ,Rhyme learns it cannot get around without reason, and the two needs to balance. It is one of the most clever books I have ever read.
I'd like to have all 3 volumes in The Secret of Nimh series, but I can just make due with the first one. Children's books always take me to a simpler time and place.
Finally, the manga Phoenix: a Tale of the Future by Osamu Tezuka. This book made me question religion. It's art is simple, but the story still grips me.
I love all these books so much. It's hard narrowing it down, but these are the ones I'd take.