Carrie Vaughn's science fiction mystery is set an unspecified period in the future in an area known as the Coast Road, somewhere on the West Coast of the former United States. About a century ago, the world suffered a profound collapse of the economy and the environment. Hundreds of millions of people died and civilization worldwide fell completely apart. The Earth is now in a recovery period -- so this is just a post-collapse novel, not a full-on post-apocalypse -- and the Coast Road is doing a lot better than most areas. A key element of the Coast Road region's rebuilding efforts is very strict birth control -- couples and household families who wish to bear children must earn the right to raise kids. Those who do are allowed to display banners at their households that symbolize this privilege. If you don't have a banner, you're not allowed to have kids. Households that don't have banners are considered, unofficially, to be less important than households that do have banners. And if you have a kid without earning a banner first, there can be serious penalties for the parents, and bannerless children can face lifelong, if unofficial and unsanctioned, discrimination.There isn't a lot of serious crime in the Coast Road communities, but it does happen periodically. So there are citizens who must sometimes take up duties as Investigators to learn who committed crimes and determine the proper punishment for the guilty. Our lead character, Enid, is one of those Investigators. She lives in the community of Haven, and she's fairly new to the profession -- she was apprenticed to an older Investigator named Tomas, and now that she's a full Investigator, he still serves as a mentor. Previously, she's investigated thefts, frauds, and other crimes, and she's helped provide disaster relief after the superstorms that periodically plague the area. But now there's a report of a suspicious death in a small, prosperous community called Pasadan, and Enid will take the lead on the investigation.In between the chapters on the investigation in Pasadan, we get flashbacks to Enid's youth, surviving a few of the aforementioned superstorms, having her first romance, and roaming between the various communities and villages of the Coast Road.As Enid and Tomas investigate the death in Pasadan, they must contend not just with determining whether or not the deceased died by accident or by murder but with a community torn by suspicion, fear, greed, and hostility, with Enid's past coming back to haunt her, with the continuing challenges facing the world rebuilding from ecological collapse, and with the possibility of more deaths on the horizon.So how's the book? Well, first, let's talk about how it is as a mystery. A lot of the details are telegraphed pretty early in the story. I mean, it'd be a pretty dull mystery if we got to the end of the book and it turned out the dead guy just tripped and fell, no murder, everyone go home. There are also strong hints given that certain characters are very shady. The bit of the mystery that's less anticipated is how many other crimes Enid ends up uncovering -- none of them are as serious as murder, but all are serious enough to require serious punishments for the households responsible. Ultimately, is the mystery fun? Is it satisfying? Does it keep the book moving along? Yes on all points.How is this as science fiction? It's really great. Not because it's full of robots and spaceships and cyberware -- the technology level on display here is significantly less advanced than what we have now. But this is speculative fiction about the future, and it does an outstanding job of imagining what the future could look like. In a number of ways, it seems like a healthier, saner way to live, especially in the aftermath of a societal collapse. People are nicer to each other and work together better, there's less violence, people are more in tune with nature, capitalism is much weaker, if not outright dead -- and there's still greed and shortsightedness and anger and resentment and discrimination. Things are better in a lot of ways, but people still suffer from the same weaknesses. Plus millions of people died! I also kept wondering if we were looking at a world getting back on steady environmental grounds again, or if it was all about to tip headlong into ecofascism. And to be honest, reading a story that leads me to speculate about what may lie in the future of the future seems like the mark of excellent science fiction.Characterization is also great. Enid and Tomas are wonderfully well-realized. Dak, Enid's first love, is a charming musician and all-around a perfectly nice person -- while still having enough selfish cad traits to make you wish he'd fall into the ocean, but not so many you forget that he actually is a decent enough person. There are dozens of other characters, named and unnamed, living in farmland, villages, fishing communities, the edges of the desert, and the ruins of cities, who we get to meet, learn what their roles are in this new human ecosystem, and find out what they think about the world around them. There's even one deceased character, Auntie Kath, the only person Enid knew who had seen the world prior to the collapse, and who we get to know through Enid's memories of Kath's stories about the old world. All told, we get a wealth of characters, most wonderfully different from one another, and we get to see the future through their eyes.I thought this was a really enjoyable book, and its themes of building a more sustainable world are going to be topical for years to come. Go check it out.