This book was an absolute joy to read. The authors provide a setting that hits all the high-points you want in a setting: fleshed-out details that make the world come alive, mysteries with competing theories that the GM can make her own, and no mechanical details so that one could run Arduise in a multitude of systems. Part of the charm is that the writers chose to have multiple, in-setting characters speaking and interacting with the material and each other.
The theme of the game is progressive post-fantasy, and this theme emanates from every page. I would describe it as a fantasy game with modern sensibilities when it comes to cultural issues. In fact, it's one of a few games that tackles these concepts head-on.
The system itself shines in the second part of the book. The mechanics are innovative and intuitive, revolving around creative problem-solving based on how your character views the world and what's important to her. The thrust of the game is that the characters are seeking to make the world a better place in some way.
I have been unable to play as of the writing of this review, but I'm looking forward to the opportunity.
The book did have some minor typos and a few editorial fixes that needed to be made, but these detract very little from the overall experience of reading the book.