While it may be true that this is not the "end all be all" of books on the subject, it comes pretty close!
The most obvious strength of the book are the clear, sharp, full colour photographs of the author's re-enactment company, showing the group in all of their meticulously recreated kit. Everything from clothing and belt pouches to arms and armour are featured, sometimes even in detailed closeups. There is nothing bad to say about the book - the quality and content are absolutely top notch.
Of course, serious reenactors should not rely solely upon this. One has to augment with detailed original sources, such as museum catalogues with details of the original artifacts, period art, and so forth. Nevertheless, given that there is a wealth of surviving material from the period (as opposed to, say, the Iron Age) and the author is a leading authority on the subject and reenactor himself, it is doubtful that anything within the covers is seriously off base.
If you are doing XVth Cent. reenactment with military aspects of any kind, you really do need this book. Rest assured it will be an indispensible part of your library. I refer constantly to my copy, if only for inspiration. At the prices this is currently being offered at, this is an absolute bargain.