Martin Fowler
OK, I must admit, I've never read a single Martin Fowler book. Lately with people talking about him like he is a god and quoting his book like it's the bible I figured I better start looking into who he is and deciding if I should be reading his books. A simple check of martinfowler.com worked like a charm. I also discovered that he has a blog, so you guys better get your aggregators open and subscribe! :-)
After reading through some of his website and checking out the reviews of his books on Amazon, I have went ahead and purchased Patterns of Enterprise Application Architecture and Refactoring. These books are extremely well reviewed on Amazon. I will have to let you know my own review once I get them and start reading.