A short, but very useful compilation of extras to help with Cold City. This is a game I still haven't run, but I still want to. The Companion sounded like it would be helpful in this, and reading it did give me a few more handles on the game.
The first chapter is game advice, with some options about how to handle secrets and narrative authority and so good extra advice on building the characters and situation.
Next is a couple of optional rules, both of which seem to me like they belong in every game. The first is to play a scene about how the character became aware of twisted technology and/or how they were recruited into the RPA. The second is an alternative way to deal with negative traits, and looks much better than the original rule.
The rest is material to use in games - how other organisations (like the CIA, GRU and others) fit into Cold City's Berlin; some places of interest in the rest of the world; more sources of inspiration.
I can't imagine this not being a useful book for anyone playing the game.