Warner and his colleagues provide detailed histories of nine affiliates of the so-called Islamic State (also known as ISIS) on the African continent. These well-informed political histories provide a fascinating view into the global reach of radical Islam. On the African continent, ISIS affiliates can be found in Algeria, Libya, and Tunisia in North Africa; Mali, Nigeria, and some of their West African neighbors; Somalia; and, to a lesser extent, the Democratic Republic of the Congo and Mozambique. Although ISIS has been in decline in the Middle East in recent years, African militant groups still seek its imprimatur to gain greater legitimacy and to win potential financial support, even though such aid has rarely materialized. Formal ties between the affiliates and the core isis organization remain tenuous and only partially developed, but the book does suggest that the Internet has proved to be a remarkably effective way for these groups to influence one another, allowing them to share tactics and rhetoric—and to indulge in their predilection for filming gruesome acts of violence.