Hilldiggers: A Novel of the Polity

A standalone novel, set in the same universe as most of Asher's other books, but without much in the way of close connections to them. Notably, all of the action takes place on a couple of human colony words outside the Polity, although two of the main protagonists do hail from there.

It's not one of Asher's best books, to be honest, having a slow start and telegraphing some of the big reveals rather too far in advance (it's pretty obvious what's going on with the quads, and where they came from, almost from the beginning). But this is made up for by the setting, with the human colonists having had to dramatically alter their biology to cope with planets that really stretch the definition of “marginally habitable”.