When I read about this book, I was ecstatic. I thought there would finally be a Pathfinder version of Heroes of Battle, one of my favorite 3.5 sourcebooks. But alas, 'tis not the case.
Instead of creating a system in which it explains how each PC can influence the battle, they focused on rules for units of troops. In fact, they only put half a page in about how an individual character moves and fights in battle, and even that was mostly devoted to explaining that they're really just a part of another unit.
That being said, it's still a good system, it's just more of a wargame than an rpg sourcebook. Personally, I think that in a rpg campaign, it would only be useful if the PCs are the generals of the army, and even then, it would simply be used as a slight change, perhaps an encounter or, if the DM and players enjoy it, perhaps an adventure.
IMO, unless the campaign is based around the players controlling a military campaign, it isn't worth the money, particularly since you can get Heroes of Battle, a much more useful sourcebook, for about $25 on Amazon.
