Fun steampunk novel of a mining machine gone berserk, leading to a walled-off Seattle full of poison gas and zombies. It's a ridiculous premise but an entertaining one, as the setting is fantastic - creepy and claustrophobic, but full of little niches for speculators and inventors to turn a profit.

For the most part the characters live up to this mad world, but the primary focus is on Briar and her teenage son Zeke. They're separated for much of the novel so it follows them separately, and the risk of split storylines is what it always is: one is frequently more enjoyable than the other. I would have preferred to stick with Briar all the way through, as she's far more interesting (and had the more interesting plot) than her son.

The twist at the end - what really happened to Leviticus Blue - is not that much of a surprise, however. It's been fairly telegraphed all the way through, and the refusal to directly address it earlier does seem a bit like stretching out the story for the sake of it. But it's still a likeable read, even so.