In this book, Alessandra Palla provides the first comprehensive investigation into the manuscript tradition of the Dionysius of Halicarnassus’ De thucydidis idiomatibus, commonly known as Epistula ad Ammaeum II. The extensive study of all the manuscripts and the innovative results allow for a new reconstruction of the stemmatical relationships between the witnesses of the Epistula. The present work demonstrates the pressing need for a historical-critical edition with a commentary, a project that Palla is currently engaged in.