In the Woods by Tana French

This is a debut mystery novel that takes place in Ireland. The main detective, Rob Ryan, is working the murder of a teenage girl from his hometown, Knocknaree, with his female partner and best friend, Cassie. Rob had 2 friends growing up in Knocknaree who disappeared. The earlier case plays into the present case. Rob is Ryan's middle name and he does not reveal his identity to his superiors but Cassie knows who he is. Cassie has a past that helps her figure out people's true selves. This is a well-written, literary book. It completely drew me in. I highly recommend it and I can't wait to get to her second book which I hear is equally excellent.