[I posted this question 7 months ago and got a lot of upvotes but no answers... hopefully the right historian will see it this time!]

From different sources I've seen mention of the period in which, due to the ravages of war, the geographically-immense city of Rome had only a fraction of its earlier population -- in the low to mid tens of thousands perhaps, living in clusters within an otherwise abandoned city. Between the last parts of the 'Gothic Wars' and the formation of the Papal States seems to be the period in which Rome the city was at its lowest, when compared to its prior prosperity.

Are there any reliable books or interesting scholarship focused on the city of Rome during this period, drawing from reliable primary sources and first-hand accounts, that give insight into what conditions in the city were like at this time? Is there anything that stands out as especially descriptive, or detailed enough that we can better understand the day-to-day of living in the city? Where and how did people live? What was their relationship to the abandoned districts of the city, and how did they view those areas?

Recognizing Roman history as a source of inspiration for works of fiction, I've read a number of books that arguably borrow from this period and circumstance. Asimov's 'Foundation' and his descriptions of post-fall Trantor; and from Tolkien through a multitude of modern authors, 'ruins of former glory' are a nearly constant theme. And, contemporary post-apocalyptic books and movies/tv regularly portray imagery of formerly great cities fallen into semi-intact abandonment, sparsely populated by survivors.

So, what exactly do we know with any confidence about the city of Rome during this period? Where can I go to better educate myself?