Biblical exegesis occupies a central place in the literature emanating from late antiquity and the early Middle Ages. It can take different forms, only one of which is the systematic verse-by-verse interpretation of books of the Bible. More often than not, it comes in more subtle guises, embedded seamlessly into texts ostensibly pertaining to other recognised genres, like historiography, onomastics, law and so forth. Although modern scholarship distinguishes principally between a number of early approaches to biblical interpretation, like the four-fold sense of Scripture, these approaches can sometimes overlap or segment into different subcategories. The elaborate taxonomy of exegesis which ensues can be a curse for some and a blessing for others. Some will be frustrated by it, while others will recognise the merit of diversity as a means for exposing something about the unique intellectual contexts in which different exegetes were operating, contexts that could have informed the choices that they made with regard to which scriptural passages they cited and how they interpreted them. Consequently, a close inspection of surviving texts can, hypothetically at least, shed light on their historical contexts. It is this principle of reverse engineering that Thomas O'Loughlin seeks to apply to Gildas's De excidio Britanniae, the only surviving, yet notoriously obscure, witness to mid sixth-century Britain. O'Loughlin styles his ambitious plan an ‘experiment in method’, a method that he makes up as he goes along, with remarkable self-reflection. However, as is often the case with idiosyncratic yet charismatic studies, this work refrains from systematically articulating methodological principles, and readers may therefore find it impossible to repeat the exercise in relation to other late antique or medieval texts. The book comprises two parts. The second and much longer is essentially a database of Gildas's quotations from the Bible, each briefly and carefully analysed, sometimes with reference to previous scholarship. Textual critics interested in the circulation of the Bible in the British Isles will welcome this meticulously-assembled appendix that offers a much-needed identification of the Bible versions that Gildas's biblical citations and allusions drew on: the Vulgate and different traditions of the Vetus Latina. The first part of the book makes use of this appendix for assessing more comprehensively Gildas's role as historian, exegete and theologian, though it would have been interesting to hear more about O'Loughlin's views on the validity of what is potentially an anachronistic generic distinction between disciplines, which the book appears implicitly to contest. As previous students of Gildas have already found, the nature of the material from De excidio Britanniae inevitably invites some non-committal and frustrating conclusions (for example, ‘does not follow to any noticeable extent an established pattern of exegesis’; ‘it is equally useless to ask questions about how he viewed his nation in relation to the original Israel’). There are, however, more positive insights, like the stress on Gildas as a sophisticated rhetorician who can be properly understood only when regarded as preacher rather than bookish theologian. Important observations by Michael Lapidge on Gildas's traditional Roman education in rhetoric are precociously developed towards painting a portrait of Gildas as ‘lawyer turned preacher’ who chided contemporary leaders and prelates. This plurality of roles again brings to mind questions of generic classification which mirror Gildas's complex intellectual personality.