Mainly books on economics, stock trading, finance, and physics (which I am terrible at, I enjoy the theory but the math is hard)
I also read the Bible.
The current book I am reading is titled The Paradox of Choice. It describes how we are less satisfied with our decisions because of all the other opporunities. The more choices, the less satisfaction.
Look at the classifieds and watch how fast people turn over good product. Not because of inherent defect, but because of all the other choices....they turnover and turnover and are never happy....because of self-doubt as a result of all the choices.