River of Darkness

River of Darkness by Rennie Airth is a post-WW1 unconventional love story that takes place during a serial murder investigation. The narrative describes the point of view of the police at first but does shift in some chapters to describing the criminal's thoughts and actions. The book won the 2000 Grand Prix de Litterature Policiere International Prize. This is the first book of a trilogy. Chances are I won't read the others. The book is more focused on the detective's personal life than I prefer, the detective himself is too needy and clinging for me, and I avoid books about sex crimes if I know that's what the story involves.

from the back of the book:

As rural England slowly emerges from World War I, a particularly vicious attack on a household in a small village leaves five butchered bodies and no explanation for the killings. Scotland Yard sends Inspector John Madden, still recovering from his own harrowing war experience and from the deaths of his wife and child. The local police dismiss the slaughter as a botched robbery, but Madden detects the signs of a madman at work. With the help of Dr. Helen Blackwell, who introduces him to the latest developments in criminal psychology, Madden sets out to identify and capture the killer, even as the murderer sets his sights on his next innocent victims.

January Magazine reviews it here. The New York Times has a review and a link to the first chapter here.