The Dry by Jane Harper (Aaron Falk #1)

WHO REALLY KILLED THE HADLER FAMILY?

I just can't understand how someone like him could do something like that.
Amid the worst drought to ravage Australia in a century, it hasn't rained in small country town Kiewarra for two years. Tensions in the community become unbearable when three members of the Hadler family are brutally murdered. Everyone thinks Luke Hadler, who committed suicide after slaughtering his wife and six-year-old son, is guilty.
Policeman Aaron Falk returns to the town of his youth for the funeral of his childhood best friend, and is unwillingly drawn into the investigation. As questions mount and suspicion spreads through the town, Falk is forced to confront the community that rejected him twenty years earlier. Because Falk and Luke Hadler shared a secret, one which Luke's death threatens to unearth. And as Falk probes deeper into the killings, secrets from his past and why he left home bubble to the surface as he questions the truth of his friend's crime.