Set in Rokugan, a mythical Feudal Japan, Clan Wars is a tabletop miniatures game, in which armies of rival factions or houses fight for honor and the privilege of defending the Emerald Throne.
Clan Wars is a miniatures game, much like WHFB. However, unlike WHFB, Clan Wars is a more complex game with added dimension and detail that the producers of Warhammer fear is above the IQ level of their target audience.
The system is smooth, detailed and has a more gritty feel that WHFB. The game has the unique and very, well cool, attribute of having only one turn. Which is to say, there is no active or passive player as there is in WHFB, but instead each turn involves equal actions by both players with simultaneous missile fire and combat. The result, while it is more work than Warhammer, is a more rewarding sense of player interactions and a much lesser feel of 'being screwed' by going second than you get in standard active/passive player games.
The only limitation of the game system seems to be the depth of the Universe, as there is, when all is said and done, only so many ways you can say Samurai with weapon X, before much of it seems the same.