Gregory's Decem Libri Historiarum, usually known in English as the History of the Franks, opens with a rapid survey from creation to the birth of Christ before settling, from around the reign of Clovis onward, into a year by year account of the Frankish kings, their wars, their marriages and their murders, interwoven with church councils, plagues, portents and the miracles worked at the tombs of local saints. Gregory wrote as a participant as much as an observer, naming himself, his sources and his own doubts in a way few chroniclers of the period attempted, and modern historians treat that transparency as one of the work's chief values: it lets a reader see how a well informed sixth century bishop assembled and weighed conflicting reports rather than presenting history as settled fact.
For generations the Histories were read as a straightforward, if gossipy, chronicle. More recent scholarship, notably Ian Wood's study of the Merovingian kingdoms, has argued that Gregory wrote with a purpose, defending the authority of bishops such as himself against royal encroachment and shaping his portraits of individual kings, Chilperic above all, to make that case. Read either way, the Histories remain the fullest surviving witness to the conversion of the Franks under Clovis and to the workings of a post-Roman kingdom still finding its own institutions, and almost everything known of Gaul in the sixth century passes through Gregory's own telling of it.