The annual Ecclesiastical History Society Book Prize is awarded for an author’s first monograph in the field of ecclesiastical history. Publishers submitted a wonderful range of volumes covering many aspects of ecclesiastical history broadly defined. The winner of the Ecclesiastical History Society’s prize for an author’s first book in the field of ecclesiastical history for 2019 is: Sean Griffin, The Liturgical Past in Byzantium and Early Rus (Cambridge, CUP. 2019) Sean Griffin’s book The Liturgical Past in Byzantium and Early Rus is a fascinating and excellently written study of the evolution of Christian historiography in early Rus. The use of liturgy as history, while owing much to previous scholarship, is innovative and terrifically thoughtful. What could be a potentially daunting array of source material is handled by the author in such a way as to guide the reader gently and authoritatively, clearly tracing the connections between liturgy and history writing. Griffin studies the so-called Russian or Kievan Primary Chronicle, a text in Old Slavonic which recounts the history of the Eastern Slavs and their early rulers in Kiev from the ninth to the twelfth centuries, usually dated to the early twelfth century, but surviving in later medieval manuscripts. It is full of particular stories about the early princes such as Vladimir, Boris and Gleb, as well as the account of their conversion to Christianity by missionaries from Byzantium. The core of Griffin’s argument is the association between Rus liturgy and history writing in which he invokes the notions of the ‘liturgical past’ and liturgical rites as a ‘public technology for creating and controlling cultural memory’. He is persuasive in his discussion of the Byzantine/Rus liturgy as a means of storing the past, constructing meaning, propagating and exploring the Christianisation of the Rus, often for political purposes, and the case he makes for the liturgy being an ‘information technology’ accessible to all levels of society. He charts the process by which the Slavonic liturgy turned the history of a dynasty into the sacred history of saints and exposes the liturgical components underpinning the myth of Christian origins for the land of the Rus. The reflections on the social and liturgical experience of monks in Kievan Rus– how their repetition of liturgical elements served to forge new historical horizons – was often moving. Griffin’s explanation of the liturgical day experienced by early Rus historians, and its effects on their categories of thought, was particularly powerful, and there are some very clever lexical arguments. He navigates his way through nearly three centuries of clearly rebarbative scholarship very professionally and courteously, and he sustains his argument convincingly throughout the book. The book is clearly an important contribution to early medieval Russian and Byzantine studies in particular, but also on the relationship between medieval historiographical, biblical, and liturgical texts. Griffin’s book did the most of all the shortlisted books we read to extend beyond its own research topic to say something wider to the discipline. He makes an energetic, even passionate, case for the vital importance of the liturgy as a source for studying premodern Christian societies. From the outset, moreover, Griffin shows how the history promulgated in the Rus Primary Chronicle continues to pervade Russian history today. Overall, Griffin’s book has important things to say about history writing, the interpretation of events, and about lived religion. In our opinion, it is an exceptional first monograph and we congratulate him on behalf of the EHS most warmly.