Scholars have long acknowledged the importance of Paul the Deacon's Homiliary, which he compiled for Charlemagne, who requested a collection of the best Patristic texts to serve as readings in what became the first royally commissioned homiliary. Yet because the many extant manuscripts up to now have remained largely unexamined, assessments of the contributions of this text to Carolingian religion—and to medieval European Christianity in general—have been speculative or based on limited evidence. Zachary Guiliano's fine study, however, confirms in remarkable detail that the Homiliary amounted to a major contribution to the Frankish reform project. Guiliano's book consists of an introduction, six chapters, a conclusion, and five appendices. In addition to providing a handlist of the numerous manuscript witnesses to Paul's Homiliary, the appendices also offer editions of those texts connected to the earliest surviving examples of the work. These include Paul's dedicatory verse (Summo apici rerum), Charlemagne's famous prefatory letter (Epistola Generalis), Paul's descriptive introduction (Incipiunt omeliae), and Paul's laudatory verse (Utere felix). The introduction examines previous attempts to reconstruct the collection's contents and the relationship of those contents to Charlemagne's Epistola Generalis, and it provides an overview of how historians of medieval preaching have understood the Homiliary. Guiliano also discusses the manuscripts, having used digital technology to uncover a total of over 410 witnesses, including more than 80 exemplars from the ninth and tenth centuries, some of which are only fragmentary.

In chapter 1, the author examines the manuscript witnesses in order to reconstruct the contents of Paul's Homiliary. The work was divided into two parts: a Winter Volume and a Summer Volume. Guiliano returns to the earliest and most reliable examples to reconstruct these volumes, building on previous reconstructions while correcting errors and adding nuance. He charts out the differences between his version and those of earlier scholars, making only a small number of changes to the Winter Volume, while renumbering nearly half of the Summer Volume's readings. Thus, having recreated the entirety of the collection, he proceeds in chapter 2 to explore how Paul framed the liturgical year in his Homiliary. In response to Charlemagne's request for eloquent and error-free readings for a variety of occasions, Paul provided an exemplary version of the Christian calendar at a time when the liturgical year was still being shaped. Thus, the Homiliary played a significant role in defining which feasts and fasts warranted celebration in the Latin west. Guiliano concludes that Paul apparently used a “Roman” Gospel lectionary from the seventh or eighth century to shape his homiliary, and he cautiously argues that the specific liturgical year reflected in Paul's collection was most likely November 797 to October 798.

Chapter 3 considers the composition of Paul's collection. Guiliano takes the approach that Paul's intentionality as a compiler cannot be overlooked. His conception of the work transformed the ancient authors’ words into his own within the context of the Carolingian reforms. Furthermore, Guiliano highlights how the authorship of Paul's text was indeed a complex affair: the collection was “a product of multiple causes and authors,” referring to Charlemagne's commission to Abbot Theudemar of Monte Cassino, Saint Benedict's miraculous aid, and Paul's work as the compiler (94). Charlemagne primarily desired the homiliary for the liturgy of his palace chapels rather than for use throughout the empire, yet his royal sponsorship helped make the work desirable in churches throughout the realm. The homiliary is also striking for its contents. Though texts appear from Ambrose, Augustine, and Jerome, the majority belonged to Bede, Gregory the Great, Leo the Great, and Maximus. Paul borrowed texts from numerous libraries to build the collection, whenever possible checking multiple copies to remove errors and produce correct, elegant readings. Finally, Guiliano argues that Paul's laudatory verse (Utere felix) was most likely composed for Charlemagne's visit to Rome in 800, which supports dating the collection to 797–798. In chapter 4, he investigates the homiliary's dissemination. Guiliano estimates that producing both volumes of the collection amounted to a major investment of material resources, the equivalent to making a complete Bible, plus one year of a scribe's labor. The author also examines literary and manuscript evidence for the collection's presence throughout the empire, noting that often the Winter and Summer Volumes traveled separately. Particular monasteries, including Tours, Reichenau and St. Gall, seem to have played a significant role in the production of some of these hefty tomes.

Many readers will likely find chapter 5 especially interesting. Here, Guiliano examines the theology in Paul's Homiliary, which he argues reflects Charlemagne's concerns. Accordingly, Paul supplied material on Trinitarian doctrine, Christology, eschatology, and ethics. The majority of the readings focus on Gospel passages, though other books appear often indirectly, making the collection a model for conducting biblical exegesis. Paul generally paired homilies from Bede and Gregory who largely analyzed Gospel verses, with sermons from Leo and Maximus who offered more straightforward explanations of doctrine. These pairings offered orthodox explanations of scripture and statements of correct doctrine, including a particularly Chalcedonian Christology. Finally, the readings provided numerous moral exemplars for the faithful to emulate for their own spiritual benefit. Chapter 6 focuses on how Paul's Homiliary was used by particular communities. Some increased the number of readings to make larger collections, while others produced an abbreviated homiliary more suitable for a preacher to carry or for other reasons. Finally, the author offers a preliminary examination of how the text seems to have been used through literary evidence, here planning to do additional research in the future. Overall, this study offers a fascinating and impressive look at Paul's Homiliary. Doubtlessly future scholarship will follow Guiliano's lead to uncover how the collection shaped Christian thought and experience in manifold ways throughout the medieval centuries.