This is by far the most thorough book ive read on battlefield tactics in the Napoleonic era. My fellow reviewer has commented that it misses the big picture but I think this is missing the point. The big picture is not the purpose of this book. There are countless books on the campaigns of napoleon so if that's what your after, look elsewhere.
This book describes the low level combat that took place between the sides during the war. It also goes into detail about the different philosophies of the nations involved and how these evolved as the war went on.
It is divided into chapters such as infantry vs infantry, cavalry etc. My favourite part of the book is his theory on the psychology of combat when two battalions meet in the field. One of his conclusions is that bayonet fights actually never took place on open ground...
This is not really for the casual reader though. It is more suited to academics, war gamers or people with a keen interest in military science. For this purpose I Think it is probably the best around.