Worth the read, but takes a while to get going. The meat of his argument is in Part II, and you can basically stop reading there without missing much.
He often seems more interested in creating a mood, a shift in perspective, rather than advancing an argument or telling a story.
3 things I learned:
- Both the Vandal conquest of Africa and the Gothic conquest of Italy were less "invasions" than power grabs by elites that had grown up on the borders of the Roman Empire and wanted to be a part of it. Those elites were elites, in part, because of intermarriage with the imperial family and having served as imperial troops in previous wars.
- Justinian, the emperor who in most histories is a valiant hero trying to reclaim Roman glory, can be seen as the man who destroyed the new stability the empire was settling into, pushing it into dissolution.
- The popularity of the monophysite variant of Christianity in the Eastern Roman lands (Egypt and Syria), and its suppression during the reign of Justinian, probably paved the way for the rapid adoption of Islam in the seventh century.