To anybody who did A-level French in the 1970s, the nature of the famous feud between Albert Camus and Jean-Paul Sartre, the twin giants of French philosophy and literature, was not only a compulsory exam question but also pretty much an incomprehensible affair. The two authors had started out as uneasy friends, drawn together by a common interest in the big issues of the day (the French Resistance, the ethics of violence, communism). They also shared an enthusiasm for women, alcohol and general carousing on the Left Bank. But before long the alliance had degenerated into a vicious and sometimes childish rivalry. 

This is when everything gets complicated. As documented with forensic precision by Andy Martin in this entertaining and occasionally dazzling book, Camus and Sartre, once the almost indivisible intellectual leaders of a generation, ended by trading insults which, for all that they were couched in the language of Hegel or