In the Woods by Tana French

In the Woods, the first title of the Dublin Murder Squad series, introduces Rob Ryan, a Dublin detective who survived a horrible event during his childhood. Keeping his past a secret from everyone but his partner Cassie, he is forced to confront these events when a new case bears startling similarities.  Rob and Cassie are not only partners, but best friends as well, and their relationship drives the story. They are flawed, yet frustratingly relatable.

There are currently 6 books in the Dublin Murder Squad series, but be warned! Each book is told from the perspective of a new main character, offering a new voice with each title. The second title, The Likeness, is narrated by Rob’s partner Cassie.  This is both maddening and enchanting – I’ve yet to read another series like this.