Art of the Duel is a highly focused supplement to the Legend of the Five Rings RPG. As the name suggests, this book gives all sorts of background on the dueling traditions of Rokugan. However, it doesn't just stick with the familiar Iaijitsu and Taryu-jiai from previous editions, but goes beyond, showcasing dozens of styles of competitions with full rules.
While most of the game text and the new schools are geared towards duels or games, that by no means restricts them. Included are some fantastic character options for most builds. Do yourself a favor and check this out.