Iranian-born scholar Vali Nasr has become one of America's leading commentators on current events in the Middle East, admired and welcomed by both media and government for his "concise and coherent" analysis (Wall Street Journal, front-page profile). In this "remarkable work" (Anderson Cooper), Nasr brilliantly dissects the political and theological antagonisms within Islam, providing a unique and objective understanding of the 1,400-year bitter struggle between Shias and Sunnis and shedding crucial light on its modern-day consequences.