It's a real page-turner of a book and I stayed up far too late to finish it in a single sitting. Although the central narrative is one long chase and there are enough fight scenes to shake a stick at, it has many and complex layers. It turns out the Surface humans are the descendants of rich and powerful men who left Earth after the pillage of resources had devastated it. And the Roof dwellers are the descendants of the people they had left behind to die. The Roof has many political factions but mostly its people are suffering and hungry, at the mercy of one extremist sect or another. It's not at all as Stopmouth had imagined and it's very difficult for him to focus on the goal of saving his Tribe.
I loved it and all fans of action-based dystopian fiction will love it too. I understand there is to be another book in this ''Bone World'' sequence - I only hope we dont don't have to wait another four years for it.
My thanks to the good people at David Fickling for sending the book.