While it might take some re-learning if you're coming from a traditional tabletop background, if you're after narrative-driven roleplaying where a character's actions can heavily dictate the course of a scene, no one does it quite like Schema. It's light, it's unique, it's flexible (if you're willing to be a little creative and take the time to set up your own variations of the rules), and the depth of things that can happen from a given roll is immense. Think Apocalypse World's engine, but without the limitation of specific moves and rigid character roles. What's more, you can add just about anything you want and make it work if you try. For example, the system doesn't track health naturally, but if you want to, it doesn't require rewiring the rules. Just track it with some tokens and you're good to go!
The real beauty of Schema is that you can make most any task as complex or as simple as you want, and you can do anything you want without the need for an exhaustive list of specific actions you can take in a given situation. It allows me to zoom in and out pretty seamlessly, handling everything from intense duels between generals to grand scale campaign strategy without bloating the game. You'll need to sort of reverse engineer the system before you can really make it happen, but as the entire book is less than 30 pages, this doesn't take long.
The core system is ingenius: Every roll that matters is a combination of "stakes"; potential dangers, good things, and/or automatic effects that come together to dictate the outcome. With this basic system, you can turn just about anything into a sort of dramatic vignette in which the result could potentially feature unintended consequences or interesting new opportunities, regardless of success or failure. That core principle is what makes this engine so wonderful. It's simple, yet so deep.
I'm still finding my footing with it for my very specific needs, but at its core, it's just really fun to play for someone like me, who favors sandbox-style gaming. Once you read over the rules (which will take all of five minutes), it really opens up as you find new ways to make use of the mechanics. For instance, I was able to create a mass combat system using a combination of stakes for the strategy phase, and another for the actual battle that's rolled repeatedly until one side has won out. I track forces with tokens for both sides and the swing of momentum, using one token that can shift between sides in a tug-of-war sort of way. This is an example of something that isn't explicitly in the book, but I was able to add by looking at another product from this author, Stakes for Schema.
(If you grab this, I strongly reccommend Stakes for Schema as well. It's an excellent companion piece and is Pay What You Want.)
All in all, two enthusiastic thumbs up. And my big toes as well. I had to take my shoes off for that one, which should tell you just how pleased I am with Schema.