City of the lost / Kelley Armstrong.

Enhanced descriptions from Syndetics:

Casey Duncan is a homicide detective with a secret: when she was in college, she killed a man. She was never caught, but he was the grandson of a mobster and she knows that someday this crime will catch up to her. Casey's best friend, Diana, is on the run from a violent, abusive ex-husband. When Diana's husband finds her, and Casey herself is attacked shortly after, Casey knows it's time for the two of them to disappear again.

Diana has heard of a town made for people like her, a town that takes in people on the run who want to shed their old lives. You must apply to live in Rockton and if you're accepted, it means walking away entirely from your old life, and living off the grid in the wilds of Canada: no cell phones, no Internet, no mail, no computers, very little electricity, and no way of getting in or out without the town council's approval. As a murderer, Casey isn't a good candidate, but she has something they want: She's a homicide detective, and Rockton has just had its first real murder. She and Diana are in. However, soon after arriving, Casey realizes that the identity of a murderer isn't the only secret Rockton is hiding--in fact, she starts to wonder if she and Diana might be in even more danger in Rockton than they were in their old lives.

An edgy, gripping crime audiobook from bestselling urban fantasy writer Kelley Armstrong, City of the Lost boldly announces a major new player in the crime fiction world.