The Declining Hegemon: The United States and European Defense, 1960-1990, Vol. 103 Book

Honestly, this is basically the great grandfather to military wargames (excluding the military uses of strategy and tactics via games which dates back to ancient Egypt, this was for the masses). Its a rulebook basically, in comparison to the hundreds of wargames on the market now - quite simple, but I have played a version of it and enjoyed it! The pictures in the book itself are an absolute hoot, grown men in their fancy gentlemen clothes of the time positioning their regiments of soldiers, cavalry, and canons on a lawn where croquet would normally be played. They also went so far as to make small buildings for their little wars. Certainly a niche read, but as with most of Wells' work, splendid writing style with a dose of gentlemen's wit.