This is a great little product, about 300 pages and well index. The art is sparse but whats there is quite nice.
I picked it up because I had heard about the mass combat rules, and I was quite pleased with what I found there. I'll frame this with a couple points of comparison: Diaspora gives you a strategic combat mini-game that is very close to a tactical wargame played out on a map. Reign (if you can read through the purple prose to find the mechanics) gives you an abstract system for running conflicts between companies or kingdoms of any size.
Age of Arthur lays out a system for massive battles. It probably falls somewhere in between the above to examples in terms of complexity and scope. There are turns, but no map. This is okay by me, I always have a hard time conjuring up Fate zone maps anyway -- and you could probably use one if you really wanted to. Your army size is of course significant, your general has a specific role, and your PCs and heroes even have something significant to do. I have not put it into play yet, but it reads very well and I can imagine several epic battles (and even minor scuffles between warbands) that we tried to represent at the table would have been better served with a system like this.
Another area of the book that I particularly liked was in the equipment section. Perhaps it is my particular play style, but I find that too many of the newer Fate games cleave too closely to the pulp roots of SotC in that they eschew any form of equipment, weapons, armor, etc. While that is a valid play style, I much prefer the feel created by games like this that give you some simple representations of equipment and force multiplies.
Weapons and armor are basic fare. I think the real interest is in the general use equipment and magic items. They are built with the same stunts as characters -- stunts that follow a clear and consistent rubric. Too many other Fate games throw exhaustive laundry lists of stunts at you, but all you really need is presented here: some guidelines for what a stunt can do and some guidelines to get started.
The PDF is a no-regrets impulse buy. At the price you pretty much cant go wrong, and it's free if you're buying one of the printed products with it. Also, at the time of this writing, it is available without watermarks which always makes me less hesitant to take the plunge on buying a digital product.