Conquerors and Churchmen in Norman Italy, Ashgate, 1999. (ISBN0860788032)
Montecassino and Benevento in the Middle Ages: Essays in South Italian Church History, Ashgate/Variorum, 2000. (ISBN0860788105)
The Society of Norman Italy (coécrit avec Alex Metcalfe), Brill, 2002. (ISBN9004125418)
The History of the Normans by “Amatus of Montecassino” (traduit en anglais par Prescott N. Dunbar; révisé, avec introduction et notes, par Graham A. Loud), Boydell Press, 2004. (ISBN1843830787)
The Latin Church in Norman Italy, Cambridge University Press, 2007. (ISBN1107320003)
Roger II and the Creation of the Kingdom of Sicily, Manchester University Press, 2012. (ISBN0719082021)
The Crusade of Frederick Barbarossa: The History of the Expedition of the Emperor Frederick and Related Texts, « Crusade Texts in Translation(en), 19 » (traduction en anglais des principaux récits contemporains de la croisade et de la mort de l'empereur germanique Frédéric Barberousse), Ashgate Publishing, Ltd., 2013. (ISBN1472413962)
The Age of Robert Guiscard: Southern Italy and the Northern Conquest, Routledge, 2014. (ISBN1317900235)