(Note: I have no connection to this author or book. This is a genuine 5 star review.)
It is very hard to pull of a sweeping, grand history of an entire dynasty, especially one that ruled for as long as the Capetians: 12 generations. Yet Professor Firnhaber-Baker manages to do so with flair. The narrative is clear, readable, and easily accessible for those with little or no background in the subject. It's especially impressive given that virtually all of the kings were named either Louis or Philip, and there was at least one of each in virtually every generation.
This is not just a chronicle of kings, however. The women of the dynasty, many of whom were fascinating and impressive political actors in their own right, are brought vividly to life, as are a host of siblings, courtiers, and rival barons. She sticks to the evidence (the citations are exemplary), but even given the remoteness of the period the author does manage to explore the personalities and family relationships as best she can while remaining faithful to the sources.
She also does an excellent job of using the story of the dynasty to trace the process of state formation, going from the kingdom of West Francia, in which the king was only really lord of a small domain despite being nominal overlord of a much larger one, to a kingdom of France within roughly the borders we would recognize today, in which the king held more than nominal sway over the counts and dukes whose predecessors had been virtually independent. Along the way, we see how the throne went from alternating haphazardly between a couple of families through no clear process, into one with a well-defined hereditary succession, culminating in the final years of the dynasty with the legal innovation later known as Salic Law, in which females were excluded from the French throne, which would last for the rest of the history of monarchy in France.
The author is also very balanced in terms of showing the good, the bad, and the ugly of the kings and their queens. We learn about St. Louis' piety, but also his oppression of the Jews. Starting under the regency of his mother, Blanche of Castile, we see antisemitism take root in France with murderous consequences. She also discusses the Crusades, both against Muslims in the Middle East and "heretical" Christians within France itself.
Other subjects explored are feudalism, relations between the kings and the papacy, and of course the perennially complicated relationship with the dukes of Normandy turned kings of England and dukes of Gascony.
All of this must make the book sound hopelessly dense, which is why it was such a joy to find it so easy to follow and so hard to put down.