I read a translation of Contamine's original book (which is in French), which was translated by Michael Jones. The book's a little pricey (£30), but I got a second hand copy for less than half that from Abebooks.
The scope of the book is pretty large, dealing with the military changes from the fall of the Roman Empire (in the West) until about the end of the 15th century. This is not a superficial book, as the social changes that underpin military capability and the clash between and within religions are also considered.
Reading of the way power dispersed and coalesced after the Empire fell and after Charlemagne was a revelation, and it was fascinating to read of how the Dark Age rulers sought to utilise the shattered remains of Roman thinking and structures to forge armies.
There is abundant detail, with every consideration backed up by a couple of examples (or more). Perhaps this is the Englishman in me, but it was striking to notice how the French author emphasised the importance of cavalry (specifically knights) in medieval warfare.
As society shifted from a feudal system with military service an obligation towards a world where mercenaries became more important and powerful the nature of armies changed significantly. There were also geographical quirks, with wealthy Italian cities preferring to hire mercenaries and the English having a large number of excellent archers.
The dominance of short-term, small scale raids over more prolonged wars was well-described, as was the nature of objectives. Rather than seeking to expand dominions most medieval warfare was about enriching oneself through pillage and ransoming off prisoners of war (obviously there were exceptions such as Charlemagne and the wars against the Moors in Spain).
However, the extreme density of the information and the various terms (understandable both because it's a translation and because French, English and Latin terms are all relevant for various objects and concepts) does not make it the easiest book to read at times. Certain sections (the weapons, particularly) were much easier to read but at times it did feel like something of a slog.
The back of the book has a mammoth bibliography for those looking for further reading.
If you're after a comprehensive and detailed look at medieval warfare and the society that underpinned it then this is a very good book, provided you don't mind wading through a dense level of information. It's probably only for the dedicated or those who already have a good working knowledge of the Middle Ages (I don't). Or, if knowledge were a mine then this book is a rich seam but the ore takes a bit of effort to work free.
Part of the reason I read it was to help me get more of an idea of how medieval warfare might work, and it definitely helped me get that understanding in social, financial, religious and military terms.