Abdo argues that the Arab uprisings of 2011 did not herald the beginning of a journey toward liberal democracy; instead, they rekindled deep historical and doctrinal cleavages between Shiite and Sunni Muslims. Few would argue otherwise. More controversial is her assertion that in the eyes of most Muslims in the Middle East, the Shiite-Sunni split has become even more threatening than Israel. The sectarian antagonism cannot be explained away as merely the result of political manipulation or the exploitation of superficial identities: “Sometimes,” Abdo posits, “it is all about religion.” In Bahrain, the Sunni monarchy’s discrimination against the Shiite majority is institutionalized and deliberate. The rise of Sunni jihadists in Lebanon has been the inevitable response to the persistence of a state within a state maintained by the Shiite militant group Hezbollah. But there are also intrasectarian rifts: in the 1980s, Iran’s Shiite supreme leader, Ayatollah Ruhollah Khomeini, posed a bigger threat to Shiite clerics in Iraq than did Iraq’s Sunni dictator, Saddam Hussein. Abdo’s treatment of these topics is balanced, if not particularly original. What is original is her analysis of prominent self-appointed Salafi “sheiks” and their output on Twitter, where some of them have millions of followers.