First published in Russian in 1994 and now updated and translated, this is the second in an excellent new series on Byzantium from Oxford University Press. It is particularly valuable because the author considers the history of the phenomenon labelled as ‘holy fools’ (the very origin of salos, the word used in Greek sources, is obscure) not only in Byzantium but also in Russia, where the concept retains a considerable, and wider, resonance even today. Indeed, one of his chapters is entitled ‘Iurodstvo meets modernity’ and traces the survival of the idea and the practice despite the attacks made upon it by Peter the Great and again after the Revolution. This goes on: a holy fool was named as a new martyr in 2000 and two were canonised in 1997 and 1998. The image occurs in different ways in many nineteenth-century Russian writers, and will be familiar to anyone who has read Dostoevsky. As Ivanov himself explains, the book does not explore the concept from the point of view of psychiatry, comparative religion or social analysis; rather, he gives a broadly chronological discussion of the phenomenon from its first appearance as an aspect of the rise of asceticism in early Christianity to its survival in modern Russia, without however asserting a simple continuity. The decision to act out the role of being a ‘fool for God’ had early roots, both in New Testament rhetoric about wisdom and foolishness, and in the behaviour of Cynic philosophers, and there are examples of ‘foolish’ behaviour in the literature of Egyptian and Syrian asceticism, although the first ‘classic’ example in Byzantine hagiography is Symeon of Emesa, who belonged to the sixth century, but whose Life was written in Greek using a Syriac model by a Cypriot writer in the seventh. From the ninth century there seems to have been something of a revival of holy foolery, and several such figures began to appear in the liturgical calendars. The important Life of Andrew the Fool seems to belong to the tenth century, and the eleventh-century vita of one of the most famous of Byzantine religious figures, Symeon the New Theologian, contains clear indications that the tradition remained alive and well. The tradition survived into the late Byzantine period, and Ivanov can point to an unpublished Greek inscription from a Serbian church which refers to a ‘fool for Christ’ in 1317–18. The last Byzantine example he cites is an Athonite hermit who died in 1365. It is impossible to trace a clear transmission of the idea to Russia, but it was known for example in Bulgaria, and there was a holy fool at Kiev already in the eleventh century. This is a rich and fascinating book, ably translated by Simon Franklin. By opening up an intriguing and elusive topic and bringing together an immensely wide range of material it will raise all kinds of new and fruitful questions, and that is surely the best accolade that one can give.