I'm in the middle of Ruth Scurr's biography of Robespierre, Fatal Purity, and it's very good. Obviously, I can't give you a complete review of it because I'm not done, but I would definitely recommend it to anyone looking to get a grasp on most everything that's known about the enigma who was Robespierre as well as those who want a good overview of the political, social, and economic climates of pre-Revolution provincial France and Paris up until the Thermidorian Reaction.