Yet another excellent supplement for Numenera, this one focusing on the down and dirty, the cruel and cunning, the criminal element. Like Whisper Campaigns before it, this adds some Descriptors and Foci to the mix, a variety of groups with which to flavor your campaign, and a bit more fleshing out for a specific setting within the Ninth World. Like the ten great houses in the political supplement, the crime organizations laid out all have that touch of weirdness that makes this much more than 'yet another fantasy gaming book'.
(Included is a chapter on the likes of the City Watch and those whose role it is to pursue the criminal element! Appropriately enough, the title is "Watch Keepers", which makes me think of Discworld and Sir Samuel Vimes, for no particularly clear reason. There are some descriptors and foci for the lawkeepers as well, and a number of useful organizations to give them their marching orders.)
If you intend to have a campaign involving less than legal activity, unscrupulous skullduggery of a mercantile nature, and general shenanigans that don't involve the thud and blunder of great houses butting heads with a Crown, then you probably want to pick this one up.