The period covered by this book is quite a lengthy one, stretching from the end of the Roman Empire in the 5th century through to the 10th century and the various descendants of Charlemagne. Alongside the political ambitions of three distinct individuals - Theoderic, Justinian and Charlemagne himself - we get an interesting look at the papacy even before that term was used for the first time and just how it came to such pre-eminence.
The whole period is absolutely fascinating, with self-styled emperors up against popes who are a pale shadow of the clerics we come to know in the middle ages and beyond. This is a time when just who gets to decide anything in respect of Christendom (at least Western Europe) was very much up for grabs, with Charlemagne in particular seeing himself as being in charge of everything, secular and religious alike. One particularly nice turn of phrase the author uses describes the Pope at the time as being 'vice president of prayer' and Charlemagne certainly viewed himself as divinely-appointed and therefore destined to take a more pre-eminent role than any clergyman.
Each of our would-be successors to Rome subsequently fell apart, for one reason or another, and it's here that the author pushes his hypothesis - that in the end it was the papacy which would be the most successful of Rome's heirs, but mostly because of pressure from elsewhere in Europe to take on that role, along with the authority required to make it stick. This is a very readable book, making sense of a complicated time, and I may well also end up reading the author's previous book, The Fall of the Roman Empire, at some point as a result.