This book is the publication of a Princeton PhD in the history of art completed in 2010. The theme is an in-depth investigation of how the painted portrait functioned in the early Byzantine world, and this has led to some worthwhile insights. The argument is that Christianity received the tradition of representing individuals in various artistic media from the Greco-Roman pagan world, particularly of ‘revered leaders and loved ones’. However with its different views about ‘the meaning of life’, Christianity developed different modes of thinking about portraiture. These are explored by looking at the various types of individuals who were represented, in particular Christ and the saints, bishops, monks and the emperor. The argument is worked through in four long chapters, with ample documentation to both primary and secondary sources, and a well-researched repertory of images, illustrated in 115 figures. The problem of the development of the icon has been energetically examined in recent years, and Gilbert Dagron's important account, Décrire et peindre: essaie sur le portrait iconique (Paris 2007) is fully used in this study. However a second, equally provocative study, Beat Brenk, The apse, the image and the icon (Wiesbaden 2010) has not been incorporated into the arguments. Any current reader will now want to handle these three complementary books together. The book is discursive, and too often one feels that material relevant to the arguments is tucked out of sequence into the footnotes. But there are a number of original and welcome discussions. For example the analysis of the sixth-century apse mosaics at the monastery of St Catherine at Sinai (pp. 55, 158–70) makes new and cogent points. Marsengill argues that the two portrait mosaics of Abbot Longinus and Deacon John, set between the Old and New Testament figures, are not simply there as donors of the mosaic. They are incorporated into the spiritual message of the apse with its portrayal of the Transfiguration. They are portraits, in the sense that they have the square haloes of living persons, but they are much more than that. They have become the signs of the living legacy of the Apostles. They virtually participate in the event of the Transfiguration, and their faces shine with their experience of Christ, so that they emerge as exceptional in the community of monks. To see their visual role as more fluid and complicated than simply as patrons of the mosaic is helpful, and is a good example of the aim to show the many possible nuances of what might once have been naively called portrait icons.