Book excerpt: This concise and balanced survey of heresy and inquisition in the Middle Ages examines the dynamic interplay between competing medieval notions of Christian observance, tracing the escalating confrontations between piety, reform, dissent, and Church authority between 1100 and 1500. Jennifer Kolpacoff Deane explores the diverse regional and cultural settings in which key disputes over scripture, sacraments, and spiritual hierarchies erupted, events increasingly shaped by new ecclesiastical ideas and inquisitorial procedures. Incorporating recent research and debates in the field, her analysis brings to life a compelling issue that profoundly influenced the medieval world.