This clear and useful book, intended (p. x) to be accessible to students of history and religious studies, addresses a problem which is well known to their teachers. Students need to see the evidence which supports interpretation and narrative, but today's students rarely have the familiarity with Christian teaching and practice which is assumed in such classics as ‘Stevenson-Frend’ (J. Stevenson, A new Eusebius, 1957, rev. W. H. C. Frend, 1987). Some excellent new introductions, for example Mark Humphries, Early Christianity (2006) and Morwenna Ludlow, The Early Church (2009), offer extensive source material, and there are also valuable sourcebooks, for example A. D. Lee, Pagans and Christians in late antiquity (2000) and Michael Maas, Readings in late antiquity (2nd edn, 2010). But sourcebooks inevitably take extracts out of their context, and the more wide-ranging the sourcebook, the less space there is for contextual information on authors, theology and history. Stevenson-Frend required a companion volume by Stuart Hall, Doctrine and practice in the early Church (1991; 2nd edn, 2005). The book under review avoids the widespread practice of putting sources in text boxes alongside narrative. Instead, it embeds sources (all verbal, not visual) in narrative chapters which introduce historical developments and debates, so that sources and narrative interpretation occupy almost equal space in a concise and lucid sequence of reading. Gwynn's central concern is ‘the transformation of Christianity into a world religion’ (p. 2) between the fourth and seventh centuries, so most of the material comes from the period with the richest sources. He begins with Jesus brought before Pilate and ends with glimpses of Justinian, Gregory the Great and Charlemagne. Chapters range from persecution in the late third century to the post-Roman kingdoms of western Europe in the later fifth century, including debates on the Trinity (appropriately for the author of Athanasius of Alexandria, 2012), ascetic lifestyles, saints and relics and cultural interaction. Each chapter lists further reading, which always consists of books; articles might be more widely available online, but online and web resources are not mentioned at all. Ideally, the further reading entries would be annotated (as in the bibliographical essays in the Cambridge Key Themes in Ancient History series), so that readers would know where to start for their particular needs; and the index of sources would also be annotated, to help those who are puzzled by (for example) ‘Manichaean Rescript, Collation of the Laws of Moses and Rome’ (p. 18), or even by the Theodosian Code (p. 41). But this book is already a valuable addition to resources.