Last One Out by Jane Harper

Five years ago, Ro Crowley's 21-year-old son Sam disappeared from their small town of Carralon Ridge in rural New South Wales. Since then, Ro and her husband Griff have split and she has moved to Sydney with their daughter Della, although she comes back to Carralon Ridge annually for a memorial around the time Sam was last seen. The few residents that are left in the town join the family in remembering Sam, but numbers decrease every year, since the local mine has continued to buy people's homes. In Last One Out, Harper writes a novel that's a slow burn, with tension building as she introduces all the inhabitants of the town through Ro's eyes, a mother who really wants to know what happened to her son. With a great sense of place and atmosphere, this is one of her finest, right up there with The Lost Man. Absolutely one of the best books I've read this year.