Top Tier, professional, and engaging!
This book is everything a "By Night" title should be. He gave us history, the feeling of really being in Rio, interesting characters, and plenty of reason to use the book. I don't want to give away any spoilers (I know some of us buy these things to read more than just play), but I will say that I was left wanting more. Not because it was incomplete or because there were missing pieces, but because I want to know what happens next. And that is the whole point of doing a setting book well.
Some specific parts immediately come to mind, which made it feel unique:
The Carnival and social pieces (normally I don't like all of the "social combat" rules, but these were done well especially because it feels so...natural for the setting)
Octavia (her name is almost too "on the nose", but she was a fun character to read about)
The extensive coterie/relationship charts ("Wait...that character is allied with her AND him?" Very useful to have for really getting to know what's going on before running a game in that city)
It really sets a standard to which my future projects will be measured against.