Kelley Armstrong has been a successful urban fantasy writer for years before she wrote City of the Lost. It might be billed as a sci-fi thriller but the "sci-fi" is definitely a stretch, although, it takes place so far from normal civilization that it has that feel.
Casey Duncan murdered a man. Not in the line of duty as a homicide detective, nor in self defense. She's not even sorry he's dead, although she feels guilty about the lack of guilt, so to speak. Her best friend has an abusive ex-husband who won't leave her alone. Both of them need to disappear for a while and they apply to join a hidden community off the grid. Her friend Diana has no special skills but they desperately need a detective, even one who murdered, because they may have a serial killer. Casey's job is to figure out whodunit in a town where everyone is hiding behind a fake identity to protect their pasts, and some have even bought their way in with criminal pasts far more sordid than Casey's own.