The Tiberian books are an important inflection point in Cassius Dio's Roman History. After spending fifteen books covering the period of dynasts (the rise of Pompey in book 36 to Octavian's defeat of Antony in book 51) and then several books on how Augustus set up and managed the Roman monarchy, Dio deals with the reign of Tiberius in two books, which constitute the monarchy's first steps of continuation through the mechanism of hereditary succession. Christopher Mallan takes the reader step by step through these books, providing a new translation of Books 57–58, a historical commentary on those books, plus introductory material and several appendices.

A major strength of this work, especially in comparison to other commentaries on Dio, is the detailed discussion of the reconstruction of Dio's text. M. expertly leads the reader through a discussion of the manuscript tradition, as well as the works of Xiphilinus and Zonaras, among others, and clearly lays out the often confusing nature of what we now refer to as Dio's Roman History. Relatedly, M.'s decision to clearly mark in the translation the source of each section (also mirrored in the commentary) properly shows the fragmented nature of the text, in contrast especially to Cary's Loeb edition, which presents it in many places as being much more unified than it actually is. It is too bad that the book does not also include a facing Greek text, though that is a complaint about the format of the series.

Dio, of course, was not the first to write of Tiberius’ reign, and the question of Dio's sources is a frequent, and vexing, concern. M. charts a middle course between being too prescriptive or dismissive of the source question. There is general acceptance that Dio at times follows a ‘Tacitean tradition’ but reluctance to state that Dio used Tacitus as a source (e.g. 117; though see 308, where M. does have Dio using Tacitus as a source). Like others (9–10), M. does not believe that Dio used biographical sources. Yet much of his material is clearly biographical, and at times M. calls Dio ‘Suetonian’ (e.g. 210). Ultimately the source question is difficult to answer; Dio used multiple sources, and it is hard to state exactly how he created his narrative.

Along these lines, M. is insistent, rightly, that Dio took serious control of his narrative and was not merely following a particular source. Only recently has Dio been given credit for this, and M. shows again and again how Dio shaped his material to suit the purposes of his narrative. A good example is the discussion of the mutinies in Pannonia and Germania (118–122), both in comparison to Tacitus’ account and on their own. Mallan does an excellent job steering the reader away from the general hierarchy in which Tacitus is viewed as a ‘good’ historian, in opposition to Dio's position as a ‘bad’ one. Instead, M. points out not only their differing concerns, but also their different approaches to their respective narratives (see example at 100–1).

If there is anything lacking in this volume, it is the absence of strong and direct statement of why these books are important and thus why this translation and commentary is needed. At times the Tiberian books feel cut off from the rest of Dio's text. In the discussion of the transition from Augustus to Tiberius (93–4), one would like to see more about the end of Book 56, since it is key to how Dio sets up Tiberius’ reign. References to this book are scattered elsewhere throughout the commentary, but there is little sustained discussion. Likewise, M. makes frequent reference to Maecenas’ speech in Book 52, especially in comparison with or contrast to Tiberius’ behaviour, yet he does not fully elaborate on how he thinks the speech works in the History.

There are hints throughout the commentary that these books are of particular importance (e.g. the note on the tenure of provincial command, 336). Yet just as the commentary seems to begin as if dealing with two books that are somehow separate from the History as whole, it ends with little comment on where we have come from or where we are going. A general discussion on Dio's Tiberius would be most beneficial, as it would help underscore the need for this commentary and help to situate these books within the current flourishing of scholarship on Dio.

Connected to these concerns is a theme that could also use more explication and examination in light of the History as a whole, namely Tiberius’ ‘civil’ (or ‘un-civil’) behaviour. Following especially Wallace-Hadrill JRS 72 (1982) 32–48, M. translates the term dēmotikos ‘as if under a Republic’ (160) or ‘republican style’ or similar. M. is right to note that the term means something more than ‘republican’, but does not fully explain what that might be. This is an important issue, because translating the term ‘republican’ does not appear to fit well with Dio, whose work details the failures of the Republic and who was a staunch monarchist.

For these concerns (and those of other readers, as well), this book will serve as a springboard for new ideas and help continue to push Dio scholarship further. Overall, this is an excellent work of scholarship, and we now have an expert guide to lead us through these books of Cassius Dio's History.