Haythornthwaite's Uniforms of Waterloo
A truly fantastic gem of a book. It has 80 detailed colour plates of uniforms and with each plate having two or more figures - this gives just under 200 or so uniforms. However, the hidden treasure is in the footnotes, which give precise information about uniforms or regiments not illustrated. With careful reading it's possible to build up a very accurate picture of what each unit at Waterloo looked like.
A fantastic book for anyone interested in the battle, and one which I have referred to continually.