Epithome artis epistolaris, the predominant work, is a treatise on rhetoric and letter writing based on authors and sources ranging from classical antiquity to the Renaissance. Rhegius draws strongly on Cicero, Quintilian, and Poliziano, but also references Aristotle, Plutarch, Pliny the Younger, Ovid, Juvenal, Terence, Vergil, Horace, Lucretius, Caesar, Livy, Augustine, passages from Psalms and Exodus, Albertus Magnus, Erasmus, Giorgio Valla, Ermolau Barbaro, Heinrich Bebel, Franciscus Niger, and Ulrich Zasius; many of these references are noted in the margins. The treatise explores the classical tenets of rhetoric, including inventio, dispositio, exordium, and elocutio; marginal annotations also make reference in Greek to various tools of rhetoric, including metaphor and periphrasis. Although the authorship of Epithome artis epistolaris was originally uncertain, it has been attributed to Urbanus Rhegius early in his career (Rhegius' name appears multiple times throughout the manuscript in both Hebrew and Roman letters: see f. 6r-v, 8v, 9r, 16v). The predominant work is preceded by an excerpt from a medieval comedic poem, several pages of which have been removed, and several brief writings concerning rhetoric and philosophy.