I think I stumbled on this series because of an Amazon e-book sale. This is the fourth book in the series, preceded by The Ice Princess, The Preacher, and The Stonecutter. I've read them all in order. That helps because there is a story and character progression that might be hard to follow otherwise. The Stranger is also known as The Gallows Bird. As of now, there are nine books in the series.
The series takes place in Sweden. The protagonist is Detective Patrik Hedstrom. When a local woman is killed in a single-car crash, seemingly a drunk driving accident, Patrik's gut tells him there's more to the story. He discovers that the woman was a teetotaler and that she'd been forced to drink / inhale a bottle of vodka. There are tape marks around her mouth, with a hole in the middle for a bottle neck. He also finds that there are more deaths similar to hers across Sweden. Patrik searches for a connection and finally realizes that the solution is uncomfortably close to home.
He aslo has to contend with a group of obnoxious young people who are on a reality program like MTV's Real World. They drink, they have sex, they do drugs, they have fights. They're out of control and being filmed and paid for behaving badly. One of the girls on the show is murdered.
And there's Patrik's home life. He and writer Erica are about to get married. Erica is depressed and tired. She hasn't lost the weight she gained while pregnant with their daughter Maja. She's worried about her sister Anna, who lives with them with her two children. Anna is traumatized by the domestic violence she and her children were subjected to before she killed her husband. She sleeps all day and is non-functioning.
Patrik has his hands full.