This is a fairly simplistic mechanical system, but a very rich world. If you love the Usagi books, this one is for you. If you love feudal Japanese history, culture, etc. This is for you. The book provides rules for playing any of the animal "races" as well as a number of different occupations. It even provides a fairly good list of characters for gamemasters to tie into the game. But where it really shines is how it gives a summary of Japanese history, politics, etc. through the Tokugawa Shogunate, as well as a breakdown on the different provinces of the nation.
If you want to run a Usagi game, this is a fun stand-alone book. If you are interested in running a historical campaign, this book provides enough maps and details to use as a sourcebook for any mechanical system.
For those unfamiliar with the books, the default era of Usagi Yojimbo is the first five years of the Tokugawa Shogunate (1600-1605).