The union of David Nicolle's knowledge of medieval military history and the late Angus McBride's great skill as an illustrator have produced a myriad of excellent Osprey titles, but for the plates alone I would claim this as one of my favorites.
The plates portray all facets of the French military of the time, the knights, common soldiers, artillery, and mercenaries. Several famous (or infamous) characters of the Hundred Year's War, among them Jeanne d'Arc, Bertrand du Guesclin, and Jean de Bethencourt, are marvellously illustrated as they put on their armor, command their troops, etc. Plate E's redition of a contemporary Basque warrior is also quite interesting.
The text of course, is detailed and greatly informative, although a tiny bit dull in a few places. The section on the changing French tactics over the course of the war is particularly useful. Overall, this is an essential source for a student of the Hundred Year's War, a conflict that has overall been well presented by Osprey Military Publishing.