Your Magic Circle is a game about game design.
It's 8 pages, with very strong graphic design elements, and it's really easy to read.
It's also really straightforward. You create a circumstance in which a set of rules apply, then you create those rules.
Overall, if you're a game designer, I think this is very worth checking out. If you're not a designer but you're curious about design, this is not a bad place to start? I'm not sure how Magic Circle would handle convention games and one-shots---I think it'd potentially be a lot of fun to throw together a new game with strangers---but at minimum it's a neat way of looking at the basic structure of games.