Seems like everyone is reading books about business (which I guess should be expected on a board like this). A few of my favorite books are about investing (Margin of Safety, The Most Important Thing etc.), but I generally find books about business to be a waste of time. I prefer to read about history and politics.
Currently working through Roman Revolution by Ronald Syme. Interesting insight into the personalities during the last 50 years of the Roman Republic, as well as human nature in general.