I'm currently writing a fantasy, and a central theme is collapse of a great civilization. To be most genuine I would like to understand the issues of various collapses in history to not make my book come off as contrived. Are there any good books or sources on the Rome/Byzantine collapses, or anyone have any specific insight? I don't know where to begin. So far I've looked at wikipedia as a primer, but would like to have much more indepth study. I also understand that there were a lot of political issues during the 4th crusade, but don't know much. Thanks!
The classic text regarding the very end of the fall of the Byzantine Empire is Runciman's The Fall of Constantinople. For a history book, it is surprisingly romantic and tragic, and if you're interested in themes of loss and collapse, you can do no better.
It is mostly concerned with the actual siege of Constantinople though, so the scope may be too small. I can tell you that the issues surrounding the collapse of the Byzantine Empire are impossibly complex -- it sat on the crossroads of three continents and had enemies in every direction. Even its allies couldn't be trusted to stand with Byzantium (See: The Fourth Crusade and the Venetian non-response to the siege of 1453).
Good luck on your project, I hope this was of some help to you.
It's not about the Byzantine empire, more a discretion of that factors can cause a society to collapse, but I'd recommend Collapse by Jared Diamond. He gets a lot of stick on this sub, and from people much more knowledgeable than me, but I enjoyed reading it.