I started reading Tana French's books because I wanted to get a flavor for contemporary Irish life. I'm getting that, in spades, but I'm also getting first-rate mystery stories. In the Woods
is maybe more melodramatic/action-oriented, whereas this one is more psychological, almost claustrophobic in places.
This one continues the story of Cassie Maddox, who has left the Murder Squad and gone to work in Domestic Violence after the events in the first book. She's approached by a former colleague to go undercover one more time, to assume the identity of a young woman who's been killed.
What follows is a real cat-and-mouse setup. One false move will blow Cassie's cover, while at the same time, she's starting to identify with the people she's investigating, all of whom share a house with her "character." The twists at the end are entirely satisfying, and once more, we readers are left blown away by the fallout. I will happily read anything French puts out--she's proven that the first novel wasn't a fluke.
P.S. I'm not related to her, just a happy reader who shares her name.