"Dictator's handbook" by Alastair Smith and Bruce Bueno de Mesquita and "Coup d'Etat" by Edward Luttwak. I read them both around the same time, in this order. It changed the way I look at politics in the world. In particular it completely changed the way I perceive a so called "Revolution" that happened in my country when I was a teenager (in 1989, the fell of communism). I had some hunches it was actually a coup, but was never sure. After reading "Coup d'Etat", I know it was indeed a coup (among others, it was listed as such in an appendix).