Shadowrun: Emerald City is a setting book for the Sixth World Edition of Shadowrun covering that most Shadowrun of all cities, Seattle. If you are running a Seattle-based campaign, obviously this book is going to be extremely useful while not indispensable but close. For non-seattle-based campaigns, it is a fun read and gives you some information of things that will have rippling effects on the rest of the Sixth World. However, the lack of district maps and an index do badly compromise its usability during a game.
Shadowrun: Emerald City is the Setting Book for Shadowrun’s hometown, the Metroplex of Seattle. Designed to link into the new city edition of the core and providing a detailed look at the city and its situation following the city’s declaration of independence.