To understand Nicolas Sarkozy, who has been President of France for three intense months, it helps to know the story of the human bomb. “It was in 1993, when Sarkozy was the mayor of Neuilly,” Philippe Labro, the novelist and talk-show host, recalled over lunch a week or so after Sarkozy received his first Bastille Day salute as President. (Neuilly is a small leafy suburb of Paris.)