In a clear, accessible monograph, Lawrence P. Buck traces the life of a late medieval image of a Roman monster, which many Reformation scholars know as the subject of Philip Melanchthon's The pope-ass explained (1523). But Buck shows that this incarnation was just one of the many lives of this icon. The book plots its origins as a pious warning in the aftermath of the terrible flood in 1496, when the monster was rumoured to have been washed up on the banks of the Tiber. Buck then argues with compelling, if circumstantial, evidence that the icon was appropriated by dissenters, either the Waldensians or the Bohemian Brethren, who interpreted the emblems of papal authority and monstrous features as symbolic of the AntiChrist. Buck ably describes the development of the papal AntiChrist topos in the later Middle Ages before describing its masterful deployment by Melanchthon with reference to the monster from the Tiber. The final chapter chronicles the popularity and extended use of anti-papal iconography as exhibited in Luther's later vocabulary, wonder-book literature, the French Wars of Religion and Elizabethan religious culture. Throughout, Buck displays fluency across a number of topics, from the relationships between groups of late medieval dissenters to the polemics of the Lutheran Reformation. While this book is unlikely to recast any of the big historical or historiographical questions of the late medieval/Reformation eras, none the less it offers a comprehensive and insightful exegesis of this symbol of the papal AntiChrist, one of the least forgettable images and most powerful ideas of the sixteenth century.