I was a kickstarter backer for 'You are the Dungeon' and just received my physical copy last night. I immediately sat down and ran through a season for my dungeon - the initial setup, a foray, and a fallow period- and I loved it!
The rules are very simple- a few writing prompts to get you started, graph paper and instructions to draw out your dungeon based on the prompts, then fast rules to generate adventurers and to generate events for them. After the adventurers muck up the dungeon, you have a few more writing prompts to go through how your dungeon rises again- bigger and better than before.
The concept and rules are easy enough to follow and flexible enough that I never felt limited by them- only inspired. Also, it would be easy to pull in other homebrewed subsystems- say, if you wanted to use the tarot deck to build more in depth adventurers, or if you wanted to add more events to the event generator- you could do so without any worries.
The co-op rules in the back are also flexible and easy to follow, and would make this a great little game to pull out while at the local bar or coffee shop with friends. And its also a great way to build an in depth dungeon that you can then turn around and run your favorite dungeon crawling game group through too.