The Book of Roger is a twelfth-century Arabic geographical treatise commissioned by King Roger II of Sicily and compiled by the Muslim polymath al-Idrisi. On its completion in around 1157 it was the most detailed description of the known world produced up to that point. This translation covers Sicily, the seat of King Roger’s government, along with the other parts of the Norman kingdom in the South: southern Italy, the Adriatic, and Ifriqiya, as well as the book’s preface. Presented in English translation for the first time this text offers insight into Roger s motivation in commissioning such an endeavour, and the relationship between king and scholar. A comprehensive introduction explores what this important work tells us about the Norman kingdom in the South in the Middle Ages, while a series of detailed maps will enhance the reader s appreciation of the richness of al-Idrisi s data.