Stainless Steel Rat — Harry Harrison

Jim DiGriz is caught during one of his crimes and recruited into the Special Corps. Boring, routine desk work during his probationary period results in his discovering that someone is building a battleship, thinly disguised as an industrial vessel. In the peaceful League no one has battleships anymore, so the builder of this one would be unstoppable. DiGriz' hunt for the guilty becomes a personal battle between himself and the beautiful but deadly Angelina, who is planning a coup on one of the feudal worlds. DiGriz' dilemma is whether he will turn Angelina over to the Special Corps, or join with her, since he has fallen in love with her.