Phantom by Jo Nesbo

Harry Hole, the complicated ex-policeman, had left Oslo to face his demons and start over in Hong Kong. But he's drawn back when Oleg, the son of his true love Rakel, is arrested for the murder of a drug dealer named Gusto. Harry finds that, in his absence, a potent new drug called violin has flooded the streets of Oslo, leaving a multitude of victims in its wake. He's soon dealing with corrupt cops, Russian mafia, and a host of other unsavory characters as he tries to untangle what really happened to Gusto and save the boy he loves like a son. I will say, this book has quite the convoluted plot and you really have to pay attention to keep track of who's betraying whom. And the ending made me wonder where this series will go next. But if you're a fan of the rest of this engrossing series--and how could you not love the multifaceted Harry?--you will enjoy this latest chapter. If you're new to the series, start at the beginning with The Redbreast or The Nemesis.