I haven't been able to get my group to play this yet, so I haven't seen it in action yet.
The book is beautiful. About half the book is a fairly detailed overview of the Warring States, including details of the various kingdoms, introductions to how society functioned then and there, important NPCs, and so on. The GM-only section has monsters, the Powers Behind the Thrones, a short but useful section on how to run the game, and an introductory adventure.
The system itself is quite straightforward. Roll two d10, one dark (Yin) and one light (Yang). Find the difference (it only matters if Yin or Yang is higher in combat) and add it to your attribute and skill to beat a target number.
Character creation is point-buy, with each character getting one Gift (which usually allows a reroll or a bonus to a roll once a game session) and one Weakness (where the GM can force a reroll). Characters get Taos, which allow them to do stuff like balancing on the point of a spear, or using four senses to replace the fifth, and can take magic (Internal and External Alchemy, Exorcism and Divination).
The main book only has the first four levels of the various Taos; the top two are included in the GM Screen, which isn't translated yet.
That's one reason to maybe go for the French edition over the English. There seems to be at least a few supplements out for the French version, but for the English there's nothing beyond the main book yet. My French is hideous (typical English Canadian), so I haven't seen the French edition or compared the two.
Overall, my read-through-but-not-played impression is that it's a great game for historic/fantastic China - detailed in setting, atmospheric and evocative in characters, and not too heavy a rules system.
I'd highly recommend the game. My complaint is that there isn't anything past the main book in English yet, so if the French version isn't too much more expensive that might be the one to go for.