The fourth book of Tacitus' Annals has been described as "the best that Tacitus ever wrote." It covers the years AD 23-28, starting when Tacitus noted a significant deterioration in the principate of the emperor Tiberius, and the increasingly malign influence of his "evil genius" Sejanus. R.H. Martin and A.J. Woodman present an improved text of Annals IV, explain in detail the difficulties and unusual features of Tacitus' Latin, and discuss the dramatic, structural and literary qualities of the narrative. They also discuss the political, moral and stylistic dimensions of the Roman historiographical tradition. Though intended primarily as a textbook for undergraduates and high school students, this edition will interest scholars of Latin literature and Roman history as well.