It is a classic info book. A good guide to get the basics into perspective and introduce themes to a general audience rather than an in depth or comprehensive historical reference or treatise, but I would say it also goes slightly beyond that and hits the wargamers „sweet spot“ and gets them salivating. In the words of an old football coach, „Nobody ever gets cut for spending time practising the basics“ and this my friend is a good grounding text to return to so you know you „have it right“ (see below, nicely illustrated, some 48 pages and a lovely thing to dip into): 

In combination with my recent purchases of Warlord Games Epic ACW and the Worthington Games (solitaire) Gettysburg wargame, it is a nice fit.