This is arguably my favorite L5R 4e book. Not only is it packed full of detailed, interesting information relevant to any campaign in Rokugan, it is just a pleasure to read on its own whether or not you're preparing for a campaign in Rokugan. This is a 303 page tome with eleven chapters: geography, customs, social structure, politics, the arts, money and commerce, law and order, religion, education, war, and the world beyond Rokugan, along with a glossary and an optional subsytem called Way of the Daimyo aimed at allowing players to play characters of higher status, such as daimyo, abbots, sensei, or other positions of significance. Each chapter also includes a new mechanic of some sort, sometimes more than one, and here is where you will find the rules for popular schools from previous editions like the Ikoma's Shadow, Hida Pragmatists, and Shinjo Bushi.
The first time I read this book, I couldn't put it down. I went from cover to cover in glee; the quality of the writing and presentation is just sublime. Nowadays, some 6 or 7 years later, I still love actually reading this book. When I get the notice that the PDF had been updated, I flipped through to see what changed, and I had to stop myself before I read the whole thing again because it was basically like getting it fresh. This book has helped make my games richer and my characters more interesting, and I can't recommend it enough for anyone interested in playing L5R. Because most of the info is setting info, it should even still be useful going forward into Fantasy Flight's new edition. That being said, I have some qualifications to this, some things that inhibit my enjoyment.
First is that the art is pulled primarily (or exclusively, I can't tell) from the card game. Now, the card game's art isn't bad, but it often isn't the best representation of what the setting actually looks like. Everyone wears a color-coded kimono openly declaring their clan allegiance when the text tells us this is not usually the case and that Rokugani value a variety in colors and patterns on their clothes. Plunging necklines and exposed shoulders are common, and the text tells us this would be unthinkable to the prudish, modest Rokugani. It pulls me out of the text to see fashion discussed in one segment, and there's an art piece on the next page more-or-less negating all of that. The other thing is the bookmarks don't work for me and have never worked. In fact, the non-functional bookmarks is why I can't give this the fifth star. Maybe it's just my PDF reader? I don't know. I haven't tested it out. All I know is it's aggravating.
But in the end, I still love this book. It's one of the best additions to L5R4e, and one of the best role-playing supplements out there period. You cannot go wrong with a purchase of Emerald Empire.