After 9/11, al-Qaida attracted money, initiates and prestige like no other jihadi group in history. Bin Laden achieved this feat by remaining ideologically flexible. He refused to be proscriptive on small matters of faith, avoiding the kind of disputes that had ripped apart other jihadi coalitions in the past. As it stands now, Isis has not simply eclipsed al-Qaida on the battlefields of Syria and Iraq, and in the competition for funding and new recruits. Isis has successfully launched “a coup” against al-Qaida to destroy it from within. Authors trace fragile alliances and betrayed loyalties within jihadi movement. Illuminating and detail-dense.