The late Republic is one of the most fascinating periods of history you can study, not least because the sources are so rich (albeit largely written by a bunch of self-aggrandizing aristocrats or their lackeys). But Caesar was largely a symptom of its decline and everyone can choose the seeds of destruction according to their tastes. Was it the First Slave Revolt, the Gracchi, the Social War, Marius, Sulla, the triumvirate, the optimates? Was it the lack of a common enemy after the sacks of Carthage and Corinth? Was it the unresolved tensions left over from the Conflict of Orders? Probably all of them, and you're just left to marvel, as Polybius did, that the Romans had a system that held the competing tensions in some sort of balance for as long as it did.

The angle I've most enjoyed lately is applying the framework from Robin Markwica's "Logic of Affect" to many of the figures in the build up to the civil war. Erich Gruen's "The Last Generation of the Roman Republic" is also very interesting, in that he portrays most Republican institutions (and even Caesar and Pompey's relationship) functioning quite well fairly late on. The entire standoff seemed so unnecessary and avoidable, but there's too much power and prestige at stake by the end for anybody to budge. Were I to point the finger at one man it would be Cato the Younger, but as I say, it's all personal taste at this point.