Just one book?

I just heard a great review of Mouse Guard and I’m going to use it to introduce my wife to Burning Wheel-style mechanics. The one question I have (at the moment) is this: is there more than one version of the rulebook (i.e. is the boxed set the same rules as the hardcover) and are there any adventures or supplements that are sold for this RPG?

The hardcover and the boxed set contain the same basic rules. The boxed set contains a number of expansions, though.

Thanks, Luke. This looks like the perfect thing to get my wife interested in role-playing again!