The Wealth of Nations - Adam Smith
Rework - 37 Signals
Ogilvy on Advertising / Confessions of an Advertising Man -
In fact, while reading it I would swear I read a lot of the passages in it were added in wholesale from Getting Real.
I was experiencing some serious Deja Vu while reading it. More power to 37signals for being able to sell me something I've already essentially read.