Companion volumes to specific issues in history are becoming commonplace. No doubt they fit in well with the marketing practices of publishers. How valuable they are for the academic community is, however, less clear. At the right price they may provide students with a course-book, but at $297 the Companion in question is most certainly not the right price. And there is the further question as to whether history is best taught from one textbook--there is much to be said for encouraging students to turn to a multiplicity of readings.
However, if one wants to find a reasonably up-to-date survey of the status quaestionis of most aspects of Gregory of Tours studies one will find it here. Martin Heinzelmann has already written what is the standard book on Gregory, and he divides much of what is to be found there into two chapters, on Gregory's life and on the relation of his works to Patristic writings. For the student the account of Gregory's life will no doubt be useful, but the near-absence of citation of the colossal amount of secondary literature in English is a weakness for precisely that audience. The second chapter of Heinzelmann's is more valuable.
Also providing two chapters is the editor, Alexander C. Murray--one on the chronology of Gregory's writings and of the administration of Merovingian Gaul. Murray is a combative writer, who usually has the virtue of sending the reader to alternative readings, but it is difficult to see why he should occupy as much space in a Companion volume as he does to combat an article by Marc Widdowson: nor is it clear why, in his account of Merovingian administration, he thinks it is still necessary to attack the position of Pfister, which has surely been out of vogue for at least a generation (though one could not guess as much from the footnotes).
Gregory's hagiography is the subject of two articles--a very useful survey of the texts of the Miracula by Richard Shaw, and a more general discussion of the cult of the saints by J.K. Kitchen, which concludes with a fine appendix on the relationship between the Biblical citations to be found in the prefaces to Gregory's Life of the Fathers with the ensuing narratives.
Gregory's Latin is the subject of a valuable survey by Pascale Bourgain, while a small selection of the bishop's literary sources are dealt with by Joaquîn Martínez Pizarro: most striking is his suggestion of a borrowing from Sidonius Apollinaris in Gregory's account of Leudast.
Also on the literary front is a valuable paper by Michael Roberts, which gathers together the passages in the poems of Venantius Fortunatus that are most relevant to an understanding of Gregory.
In addition to the discussions of Gregory himself, there are a group of articles that provide a political context. In particular there is an exemplary account of the politics of the late sixth century by Stefan Esders, together with useful discussions of the relations of the Frankish kingdom with the Empire and Italy by Simon Loseby (though more could surely have been made of the Epistolae Austrasicae), and with Spain by Roger Collins. The broader history of the Frankish Church is well, but very briefly, summarised by Yitzhak Hen. The archaeological context, as it is currently understood, is neatly set out by Patrick Périn.
The volume ends with two articles on the fate of Gregory's writings. Helmut Reimitz, in a paper that might usefully have been bracketed with that of Bourgain, discusses early medieval manuscripts of the Histories as evidence for the transformation of the work. For the student with too little time to read Reimitz's important monograph on the same subject, this is a valuable summary. John Contreni takes the fate of Gregory's works down to the early modern period, in a fine, but short, conclusion.
This, then, is a reasonable point of departure for anyone looking at Gregory--for the most part it provides an up-to-date survey (and occasionally it goes further). Fortunately or unfortunately, such surveys can go out of date very quickly. And there are aspects of this that were out-of-date even before it was published: the maps, for instance, are not as reliable as those to be found on the Ménestrel website (which is freely available to all). Whether expensive printed volumes are a sensible way of gathering this sort of material, however, is highly questionable. Surely an on-line publication that can be updated as the subject progresses would serve the community better?