There is a good scientific article out there called "The Later Roman Empire" by Richard Gerberding; and I'll second @ExtraNoise "SPQR" by Mary Beard (it's a good synthesis of this era in my opinion, a must have). Another good one is Rome Resurgent: War and Empire in the Age of Justinian by Peter Heter.
And for those of you more interested in fiction there is this absolute masterpiece by Marguerite Yourcenar "Memoirs of Hadrian". Read it, you won't be disappointed.
And for those of you more interested in fiction there is this absolute masterpiece by Marguerite Yourcenar "Memoirs of Hadrian". Read it, you won't be disappointed.