pg has said that he considers How to Win Friends and Influence People to be the most inspiring book on leadership[0]. I think it's especially helpful for hackers, because it basically lays out instructions for how to meet (and then exceed) people's social expectations. A lot of non-hackers seem to have learned those skills in middle school, while many of us were busy learning other skills. Learning to "play along" and meet expectations is enormously valuable, in business and in life.
I had a bit of an aversion to the premise of the book at first, because it seemed manipulative to me somehow ("winning" and "influencing" people, ie. thinking of them as systems and trying to "hack" them) but I eventually came to see how narcissistic that was--I am not superhuman and cannot exert mind control, so any social "hacking" is really just using the system the way it is designed to be used. At the end of the day, most of Carnegie's advice boils down to being a nice person and putting yourself in other people's shoes often, but with examples of how that sort of behavior can be beneficial to you.