Really great. Although I see that some people here consider that this setting "destroys" the Fantasy, in my case I find that it is amazingly well thought. It is so rare to have under the eyes a read that really pushes the reflexion about how is supposed to work a fantasy world while creating tons of jokes about the unstable and unreliant rules structuring it, all in all with a light tone. I really do find this fresh and funny. It is a breath after so many fantasy scenarios where obviously nothing would have been able to function without the holy power of the scenario (crazy abusive nobles, early feudal hierarchies and worlds with architecture and social organizations from the "Grand Siècle", late Old Regime uniforms with swords, and other aesthetic thingies that -in my case again- just destroy my suspension of disbelief, etc.).Not gonna say that everything should be similar to this. But It's pleasant, sometimes to read a manga where the author tries in his funny way to explain how is supposed to just work.
If you share the same mindset, you will probably like it.