The extant books of Ammianus Marcellinus' Res Gestae cover the deeds of emperors and high officials in the quarter-century between 353 and 378 CE. The work is adorned with all the apparatus of classical historiography: prefaces, digressions, set speeches, battles and sieges, treason trials, and natural disasters. Yet for the historian of Latin historiography, or the compiler of a companion to it, Ammianus is an awkward fit. Many general works on the Roman historians stop over two and a half centuries earlier with Tacitus: a fine climax, and an inept ending. One of the more notable twentieth-century contributions to Ammianus scholarship, Edward Thompson's The Historical Work of Ammianus Marcellinus (1947), opens with the thought that “for every reader of his work nowadays there are a thousand readers of Sallust, Livy or Tacitus.” This was probably never true, and the vast expansion of interest in the late Roman world ensures that scholarship on Ammianus is now quite as hard to keep up with as on the other three great Roman historians. But what was and remains true is that Ammianus is terra incognita for most classicists, including many historiographical specialists.