I plan on downloading a bunch for the train, but what are some good ones? I may give The Art of War by Sun Tzu a try, but I'm really looking for something more abstract. Discussion of e-books that cost money is also welcome, but they have to be truly mind-blowing/phenomenal.
Both fiction and non-fiction appeal to me. I'd say I'm into the "liberal arts", but I'll find just about anything fascinating as long as it's well written and goes beyond conventional knowledge.