In this volume Patricia Rumsey uses the Nauigatio Sancti Brendani abbatis and the Teaching of Máel Rúain and the Rule of the Céli Dé to discuss the different ways in which two eighth- and ninth-century Irish monastic groups understood sacred time. The analysis examines the concept of time and the development of the Liturgy of the Hours as Christian prayer. Rumsey discusses and challenges the existing literature on the three subjects, highlighting that, although a fictional narrative, the Nauigatio (dating from the ninth century) is rich in scriptural, theological and liturgical material, which, on close analysis, presents a colourful depiction of monastic practice that Brendan continued on his voyage to the Terra repromissionis sanctorum (the promised land of the saints) and which forms the framework of Brendan's journeys; in this regard, the monks of the Nauigatio saw time as fundamentally holy. By contrast, the movement described as the ‘Céli Dé’ observed that time was an aspect of the fallen world that needed sanctification through prayer and the practice of the liturgy. Amongst the variety of concepts of time discussed in his comprehensive study, Rumsey considers the representation of time in relation to the Apocalypse and how the Liturgy of the Hours was celebrated by the monks of the Nauigatio and the Céli Dé with their different theological positions; the volume also examines the practical aspects of the importance of the Liturgy of the Hours and the structure of the office through the Liturgical Day, the Liturgical Year and Liturgical Prayer; finally, it looks at the significance of the Terra repromissionis sanctorum to the monks of the Naugatio and the Kingdom of Heaven to those of the Céli Dé. Through her contribution to understanding the early Irish monastic practices, Rumsey explores and interprets significant scenes from the Nauigatio. As a specialist on Brendan, rather than liturgy, I found some of these to be particularly noteworthy, including her observations concerning the non-judgemental philosophy of the author of the Nauigatio, through allowing Judas Iscariot a respite from Hell, and her discussion on the neutral angels (which is included in an appendix, along with a discussion of liturgical and scriptural allusions to Easter in the Nauigatio), the blinding cloud on the Island of the Three Choirs and the evidence that is presented concerning the mysterious procurator who assists the monks on the journey and the suggestion that he is an allegory for Christ who leads the monks to the Terra repromissionis sanctorum. Rumsey's work is immensely readable and is a valuable contribution to the study of the Nauigatio and our understanding of the development of Irish Christianity.