This is an excellent overview, which accurately (or, at least, cogently) captures the trends swirling in the wake of the decline and final collapse of the Western part of the Roman empire.

It is not quite a definitive work which leaves the reader with a firm bridging of the gap between Roman rule and the precursors of each of the modern European states - but it comes closer to accomplishing this goal than anything I've read on this subject (I have an interest in late antiquity).

This work needs to be read in conjunction with a host of others for a fuller picture. I recommend the superb history of Byzantium by John Julius Norwich and "Narses - Hammer of the Goths", which is a little harder to find.

The author also uses an easy, relaxed prose which strangely helps to concentrate on the mass of details which must be absorbed to make sense of the proceedings.

Although not the entire mosaic, I would recommend this book as its centrepiece on the subject.