Here are some of the books that have been influential for me:

Holy Bible - The Bible is the all-time best selling book. By a wide margin. Of course, this page has nothing to do with popularity. It's a page about books that have influenced me. The Bible is the all-time most influential book for me. By a wide margin. I've studied the Bible incomparably more than any other book (including Calc. 3 and Thermodynamics) and I'm personally compelled to believe that the Bible is good and true because it comes from a great God who is truth. Not that God wrote the book and hit print. I believe that He inspired writers so that they chose the words and He chose the message. It's not an epic book, it's The epic book. It explains the past, answers the 'Whys?' of today, and foretells what is to come. As I continue this description, I'm feeling like I can't properly describe the Bible at all on one hand and that I could go on describing the Bible for pages and pages on the other. I'll just leave you with a reference for my favorite passage: Matthew 18:3-5.
Margin - Make no mistake, this is a counter-cultural book. I was fortunate enough to hear the author, Richard Swenson, M.D., speak at a retreat I attended in the fall of 2001. For me, it was perfect timing because I had been at a 'real' job for a little over a year. I had been getting by with relatively few possessions and planning at some point to own more. In general, it felt like the sooner I could get the possessions, the better and the more I could get, the better. The timing was perfect in the sense that, while I wanted more stuff, I really didn't have that much. Dr. Swenson pointed out that everything that we 'own' requires maintenance (e.g. cleaning, storage space, insurance, repairs, tuning, registration fees). I recognized that I already had enough stuff so I decided that I would make a concerted effort to avoid further accumulation. Practically, when I come home with a new pair of jeans, I get rid of an old pair. Same goes for a new television, computer ... you get the idea. After years of this, I've come to recognize Margin as one of the most influential and valuable books I've read. I highly recommend it to anyone that feels like they need more money, energy, or time.
Radical Reformission - Christians and, by association, Jesus himself are often seen as weak, bland, hypersensitive (e.g. "I was disturbed by the harsh language."), irrelevant, and on and on. While a pile of self-proclaimed Christians probably fit this description to a tee, Jesus never did and He absolutely doesn't today. The Bible is clear about this point. Pastor Mark Driscoll does a masterful job of vividly painting the person of Jesus both in incarnation (as He was on earth) and in exultation (after ascension back to heaven) in a variety of his books and sermons. It's been a tremendous encouragement to me to be freshly reminded of the example, authority, and call of Jesus. In Radical reformission, Pastor Driscoll applies these broad, biblical teachings to the privilege Christians have of sharing the news of Jesus to all the peoples on all the earth and that the authentic message must be shared in a way that is sensible to the culture of the people being reached. It sounds simple, and it is, but his writing is rare and potent.
Atlas Shrugged - More to come.
Maiden Voyage - More to come.
Bulletproof Diet - More to come.