This book focuses on a kind of writing which was new in the fourteenth century: intellectual treatises dedicated to defining and condemning superstition. Although churchmen had written about superstition for centuries, Michael Bailey argues that the fourteenth and fifteenth centuries witnessed an increased level of interest in the topic among educated clergy, which manifested itself in a series of treatises written at courts and universities. His book is primarily a work of intellectual history, which seeks to trace how concepts of superstition developed in these treatises, while also placing them in their wider context. This was a period which saw important changes in attitudes to magic, including rising concerns about the practice of magic and astrology at court; a church reform movement which promoted practical moral theology and sought to ensure that the common people were practising only legitimate forms of ritual; and the first witch trials. As he relates the treatises to these wider developments, Bailey traces very carefully the differences of emphasis and tone between his different writers, and argues for a gradual change in attitudes rather than an intellectual revolution or a clear increase in concern about superstition to match the growing concerns about witchcraft. Instead he emphasises the diversity of views that existed throughout the period, and the individual concerns which informed the work of different writers. This focus on superstition, rather than the much more frequently studied witchcraft, allows him to offer a new perspective even on well-known texts. Thus Bailey uncovers some surprising areas of tolerance even in the notorious Malleus maleficarum, showing how in his eagerness to condemn witchcraft, its author Heinrich Kramer was prepared to permit a wide range of popular ritual practices which were designed to guard against witches, even when these might appear ‘superstitious’. The final chapter of the book moves out from detailed discussion of the superstition treatises to examine a much wider question: did the early modern period represent a sharp break in attitudes to superstition, as sometimes suggested by scholars who argue for the ‘disenchantment of the world’ in this period? Here Bailey argues that the situation is complex. On the one hand critiques of superstition continued to draw on the same medieval authorities well into the early modern period. On the other, and perhaps more surprisingly, the medieval treatises on superstition are in certain respects very ‘modern’: for example in their willingness to see superstition as a corruption of both legitimate religion and legitimate science. There is therefore much of interest in this nuanced and subtle book both for medievalists and for those working on the religious and intellectual history of later periods.