There are two other contemporary sources - the Chronicle of Marcellinus Comes and the Chronicle of John Malalas, both of them are recently translated in recent decades so you should be able to find them in a university library. Extra information is preserved in the Paschal Chronicle from the seventh century and the Chronicle of Theophanes Confessor from the ninth century, again, both have recent English translations, though I do not recommend Turtledove's translation of Theophanes.

These sources add several pieces of information to Procopius' account:

• Marcellinus Comes, who wrote earlier than Procopius, claimed that the riot was an usurpation attempt by Hypatius from the start. This might be because Marcellinus was basically regurgitating imperial propaganda though, whereas Procopius was writing much later and so there was no longer a need for Hypatius' reputation to be blackened.

• John Malalas' account depicted a much bolder Justinian who personally visited the rioters to try to calm them down (he failed). It also had less emphasis on Belisarius than Procopius, which is to be expected since Procopius stated outright that Belisarius was his patron.

• The Paschal Chronicle has a lacuna for the first part of the riots, so we don't really know what it said about the riots' origins. It does mention that Justinian had ordered extra troops to move into Constantinople to contain the riots, so again it counters Procopius' depiction of a Justinian paralysed by fear.

• Theophanes Confessor's account included a curious addition to the tale, a brief dialogue between faction members about the cruelty of the eunuch official Calopodius. It may be something randomly inserted into the narrative by a careless scribe, as in the dialogue the factions hate each other, yet after this the factions started to riot in unison. Or its a piece of genuine historical information that indicates the fluid loyalties of faction members, as some historians have suggested that this is remnant from an unabridged version of Malalas' Chronicle

As for modern interpretations, Alan Cameron's Circus Factions is the best book on how the factions worked. Peter Bell's Social Conflict in the Age of Justinian also covers this in some detail, but it approached the problem from a sociological perspective rather than a historical one, which I personally found quite difficult to digest. There aren't any books dealing specifically with the riots, so you'll have to make do with short sections in Peter Sarris' Empires of Faith or John Moorhead's Justinian, though if you can access academic journals I can give you a few more recommendations. It is also worth reading up on Procopius, as he is a very problematic author. First try Averil Cameron's Procopius and the sixth century, then Kaldellis' Procopius of Caesarea: Tyranny, History, and Philosophy at the End of Antiquity, which should give you a basic overview of the two most influential approaches to the historian (Kaldellis' idea isn't very popular, but it is fun to read and created a lot of debate).

Let me know if you have any more questions :)