Historians, when writing for the general public, don’t normally draw back the curtains on what they do. They tell the story of what happened, when it happened and who did what, but they don’t spend ages going through the painstaking work that allowed them to tell this story.

In Oathbreakers, Gabriele and Perry do something different: they pull back the historical curtains. While the book sets out to tell the history of the bitter civil conflict between the children and grandchildren of Charlemagne that tore apart the Carolingian Empire, it’s a book that also reveals how historians interrogate their sources to try to get at the real story of what happened.

While the history of the falling out between the heirs of Charlemagne is dramatic in itself, just as much of the tension in the book comes from the authors’ treatment of their sources. As Gabriele and Perry examine the sources of their history, the writers’ description of their methods also allows the reader to evaluate what they are doing. For, of course, just as the original annalists were telling a story with a view to its effect, historians work with their own set of assumptions and presuppositions. It’s just rare for these to be presented to the reader, explicitly and implicitly.

As such, Oathbreakers is both an excellent history of the division and conflict that, eventually, produced France and Germany but also a chance for readers to understand how historians come to these conclusions and agree, or disagree, with their conclusions.