Their Secrets Have Secrets. Easily a great line in The Avengers (the Marvel version, you Imperialists) is when Tony Stark is speaking of Nick Fury and says "his secrets have secrets" - which is absolutely true, both in The Avengers and this book. If you enjoy semi-slow burn (to start) almost disaster movie type suspense, where everything starts off a touch slow and normal ish before completely fucking unravelling... this is exactly the kind of book you're going to enjoy.
The other great thing about this, to me, was how well Mercer used the setting she created to create an atypical emergency situation. Without giving anything away, let's just say that it put an interesting spin on a couple of fairly worn concepts and made everything seem newer and much more intriguing in the process.
Ultimately one of those books you're going to be reading deep into the night, because "one more chapter" will never be enough.
Very much recommended.