It pains me to say that I was disappointed with this product. I've been a fan of Bill Webb's product line since the earliest days of Necromancer Games -- but The Sword Of Air (in my opinion) lacks the inherent panache which has traditionally set the Webb stuff apart from all the other old-school offerings based on somebody's homebrew campaign world. Given that the product is not exactly cheap as PDFs go, this is a purchase I personally regret.
For the most part, this product reads like a huge chunk of open-world game content set in Webb's "Lost Lands" campaign world. I say "open world" because while there is a questline in play, the story goes out of its way to provide a broad context (and broad content) for adventuring, rather than leading the players by the nose through pre-scripted steps to the quest objective.
So, the content is definitely there if you enjoy the Necromancer/Frog God style of game world -- there are a lot of pages in this PDF, to be sure -- but there is also an inescapable sense of the product preaching to the converted. If you already like Webb's gameworld, and the publisher's general style of content, then you'll probably like The Sword Of Air -- but there's very little here that stood out as particularly useful to me as someone who runs games, and has to convince others to spend time playing in them.
If I had to "pitch" this product to my players as something I could run for them, I'd be hard-pressed to find a particular aspect of the product which could draw their interest, and make them want to play this instead of something else. Don't get me wrong -- this product contains serviceable content throughout, and there is a lot of it, but we've seen this kind of content before. Sometimes, we've seen it before from Necromancer and Frog God, specifically. So, if you and your players are already huge fans, you'll love this, but it can be a harder sell to those gamers who aren't specifically fans of Webb's line.
The thing which probably disappointed me most in The Sword Of Air was the noticeable drop in production values. Necromancer and Frog God have always been known for having a slick visual style built into their products -- a panache which helps "sell" the adventure to the Dungeon Master, and through him or her, to the players. While the cover of The Sword Of Air is gorgeous, and some of the interior art is definitely up to the company's usual standards, the encounter maps are ... well, "unimpressive" is themost polite term I could use here. I was actually shocked when I first saw these. The overland maps (what few there are) are generally good, though.
So, my opinion -- if you and your players are already big fans of all things Necromancer/Frog God, you'll probably love this, and it will be worth the cost.
If not, though, I'm not sure there's enough unique and noteworthy content in The Sword Of Air to warrant a purchase at the going price. I already know that most of what's here won't be of particular use to any of my own game campaigns.
Call my opinion a Three Out Of Five, then. If you love the company's work, you'll likely love The Sword Of Air too. If you're simply looking for something new and noteworthy, there are probably better, more cost-effective options out there -- some of them from the Necromancer/Frog God product lines themselves.