Thanks for the info! Is there a release date for the revised edition yet? All I've seen at this point is "Summer 2008." I guess GenCon is only a few weeks away, so if it's being released at the convention...
General release will be as soon as they can manage after GenCon. Masters of Court has been released already, but is not available at Amazon yet. They are very slow to get on Amazon, which is pretty much where I buy all my RPG books.
Master of Courts should be an awesome resource on courtly intrigue in the Rokugan setting, which is just as deadly as sword play, btw, and often loses or saves the lives of thousands with a single word. So in reality, political play is far more deadly. A samurai may kill or save hundreds, maybe thousands, in their career. A Courtier will likely effect millions if they have a long career.
If you get into it, hunt down Creatures of Rokugan, Emerald Empire (getting hard to find on line), Prayers and Treasures (explains and fleshes out Rokugan magic), and probably Masters of Court.
The prior Poster saying you only need the core book is pretty accurate, however these books flesh out dimensions I think make them worth picking up.
However, every book has such great fluff, and adds such great elements, I find them all worth getting.
Still, start with the core, and make your decisions from there.