What's The Best Book You've Ever Read?

Someone asked me "What is the title of the best book you have ever read and why?" 


My "best book" shifts as I read more and more and develop more and more.  


Right now I am reading one of Joel Olsteins' books: Make Every Day a Friday...as well as Black Water, which is quite amazing.  

I also started "What Would Napoleon Hill do?"

What is the best book you've read?  


Let's post recommendations of all the best books for everyone!