Well it's not like me to promote anything, but I've recently just bought a book publish by "Histoire & Collections" book number 4 (The French Imperial Guard, Cavalry 1804-1815).
In the book there's a lot (I really mean a lot) of full colour plates on uniforms and some plates comes with full illustrated rank insignia. Book 1 & 2 is about American Civil War while book 3 is about French Imperial Guards, Infantry, so far my book 4 is the latest publication.
I personally think it's the next best thing than Osprey's series.
