In this lucid and stimulating study, Brent Nongbri argues that ‘religion’ is not a natural or universal category, but a modern invention, ‘born out of a mix of Christian disputes about truth, European colonial exploits, and the formation of nation-states’. No ancient language, he points out, has a term that corresponds to any modern definition of ‘religion’. It is doubtful whether any ancient culture distinguished clearly between ‘religious’ and ‘secular’ spheres of life. The widespread, modern western understanding of religions as ‘apolitical paths to individual salvation’, which is derived largely from Protestant Christianity, is a poor fit with the many ancient and modern societies in which religiosity is deeply socially, politically and culturally embedded, which focus more on the group than the individual, and/or in which salvation is not a central concept. Nongbri examines some Greek, Roman and Arabic terms that are often translated ‘religion’, showing how such translation misrepresents the meanings of the originals in diverse ways. He discusses a number of authors and texts which have been identified as giving birth to the concept of religion (2 Maccabees, Cicero's religious writings, Eusebius, and the Qur'an), and argues that none of them does so. He traces the evolution of the idea of religion through pre-modern Christian debates about heresies, the conflicts of the Reformation, the imperialist West's discovery of the very different traditions of the East, and the application of approaches drawn from anthropology to the ancient world. Finally, Nongbri argues that rather than taking ‘religion’ for granted as a category, we should seek to understand why scholars have invested in certain definitions of it. This need not prevent us from using religion as a concept with which to study traditions and practices other than those of modern western Protestantism, but it should help us to be more aware of its etic status and its interpretative limitations. Nongbri covers a great deal of ground in 230 pages, and the argument is inevitably drawn in broad strokes rather than fine detail. Given that his central claim is not a new one (and he does not suggest that it is), Nongbri's contribution to the debate lies in his readings of particular texts, his response to other scholars' arguments, and his identification of the key contexts in which the concept of a religion gradually emerged. That being so, one might wish for more detailed discussions of the important texts, more specific engagement with the arguments of other scholars, and more detailed accounts of those key contexts. Specialists will find things with which to disagree even in the brief interpretations that Nongbri offers. On the other hand, Nongbri's breadth of vision is such that even specialists are likely to find something new in his case studies and argument to stimulate reflection, while students will find his trenchant and accessible writing a useful introduction to an important debate.