Emotionally, City of Pearl ends with a maxim from; it's one character's interpretation of a second's hard choices as acceptably moral, even heroically moral. It's a nice yardstick to set next to the whole story in hindsight, where it would have been too didactic during the action.
The action is moved by the slow and horrible collapse of Terran governments under environmental disaster, but mostly occurs on another planet. bearing a human colony but managed by a race given to low-impact environmental absolutism (their cities are, ideally, invisible). There are other sentient species, including some cephalopods, who I'd like to hear more of.
There's someism in the heroine, who is a hard-core hard-case environmental enforcer, a police officer who impresses Marines. The Cassini Division idea about "someone has to do the dirty work, so I might as well" fits her like a T-shirt.
ISBN: 0060541695So wrote clew in SF&F.