The Great Clans is an amazingly useful sourcebook for Legends of the Five Rings, while not quite a necessity to own to run or play the game it comes close. It expands on both the Great Clans and the world they have made, providing a wealth of information and even some useful new mechanics.
The Great Clans, a sourcebook for the Legends of the Five Rings RPG (3rd edition) is a 306-page PDF (304 pages if you remove the cover), written by Shawn Carman, Rob Hobart, Brian Yoon, Kevin Blake, Nancy Sauer, Ryan Reese, Jacob Ross, Max Lemaire, Dave Laderoute, Rusty Priske, Mike Brodu, and Daniel Briscoe and published by AEG.
The layout is a straightforward design taken directly from the print version of the book, with a 2-column layout (and occasional one column commentary). The Great Class is lavishly illustrated with full color art throughout. The table of contents is complete and there is an index as well, so finding what you are looking for should be easy but you have to use that as the PDF book-marking only takes you to the start of each chapter.
As it says, this book is full of information on the nine Great Clans of the Empire of Rokugan. Primary, it is all general information, history of the clan, background of the families, useful cultural notes and roleplaying hooks. However, each family gets some new schools, new paths, new kata and additional ancestors for those who like mechanics to spice up things.
The background information on the clans is amazingly useful for both players and game masters, expanding on the very brief sections in the core book. In each clan’s section there is cultural information, such as courtly affairs in the Crane section and additional information on the tradition of ancestor worship in the Lion section.
Appendices handle the new(ish) Spider Clan, the various Vassal families of the great clans and the return of the heritage tables. Heritage tables are a way to give a character an additional roleplaying hook that may be positive, negative or a mixture of the two expressed as the character’s linage (such as an ancestor was a famous poet or a well-known coward). Each Clan gets its own table, there are some slight imbalances between the clans until you come to the Spider, who get two tables of bonuses and one of mixed good and bad things, but even then the good side far outweighs the bad. The Spider tables should not be used as written, as they are just a guaranteed mechanic bonus for the character, unlike all of the other heritage tables.
Disclosure: As a featured reviewer for RPGNow/DriveThroughRPG, I received my copy of this product for free from the publisher for the purpose of this review. Also, I am friends with several of the authors, but I hope that has not shaded my opinion of the product.