Although it has been thirty years since Timothy Barnes last published a book bearing the name of Constantine in its title, it is clear that the life and reign of the first Christian emperor has never ceased to occupy his intellectual energies. In the present volume Barnes draws together his prodigious body of work on the subject – more than fifty of his articles and monographs are listed in the bibliography – into a concise narrative, which challenges dominant scholarly opinions on a number of issues. Some themes will be familiar to readers of Barnes's work, such as his defence of the reliability of Lactantius and Eusebius on certain key points (pp. 6–7 and passim), his denial that Constantine began his reign as a usurper (pp. 62–6) and his vehement repudiation of the phrase ‘Edict of Milan’ (pp. 93–7). One of the central claims of the book, however, is buttressed by entirely new evidence, namely Kevin Wilkinson's redating of the epigrammatist Palladas to Constantine's reign (pp. 13–16). Barnes had earlier argued that Constantine's Christian convictions were stronger than usually allowed, and he had been chastised for accepting Eusebius’ report that the emperor had banned sacrificing animals to the gods. He sharpens his case in the present volume, using the poetry of the pagan Palladas to confirm the veracity of Eusebius’ report and to argue that Constantinople was founded as a ‘Christian city, totally free of any trace of paganism’ (p. 127). Constantine emerges from Barnes's account as a ruler fully committed to the transformation of the Roman Empire into a Christian empire, who was restrained only by the conviction that time, and not compulsion, would accomplish the goal. The book is divided into seven chapters and an epilogue (and the usual cluster of appendices). After an unsurprisingly polemical account of modern scholarship, Barnes begins his narrative with the career of Constantine's father and proceeds in a mostly linear fashion to the emperor's death and final dynastic plans. It is a tour de force. Barnes's frequent digressions into scholarly controversies shed light on centuries of scholarship, and his careful framing of problems, judicious use of sources and close reading demand that his conclusions be seriously reckoned with. His command of the literature is masterful. The downside of this approach is that the flow of the narrative is often impeded, making the book a difficult read for non-specialists. Moreover, some digressions, such as his critique of the late Henry Chadwick for doubting Origen's self-castration (pp. 141–2), seem out of place and needlessly uncharitable. One could also quibble that Barnes too frequently directs readers to his articles for source information that could profitably be included in the notes. But those are minor critiques. His portrait of Constantine is convincing, particularly his claim that the emperor's agenda included an aggressive promotion of Christianity, which was executed with great political skill. This fine book is a significant achievement in a fertile era of Constantinian studies.