There are really two things going on in the former Roman Empire during this period: Germanic migrations/wars and the Byzantine Empire. Malcolm Todd's book 'The Early Germans' is a good book on the former subject. I would also recommend Norwich on Byzantium, and Herrin's book on it has been very well-received, although most of the book covers a later period.
Peter Heather has written a book called Empires and Barbarians. I haven't read it, but Heather is a renowned historian and the book seems to have been well-received.

John Julius Norwich’s stuff whilst not academic per say gives a very good overview of the period and is very easy to read