Taken as a mystery/thriller, this was a good book with a frightening, complex, and satisfying plot that I didn't want to stop reading, and mostly terrific characters. In particular, the detective and her daughter were nicely drawn, with a relationship that came across as absolutely authentic. The story is set in Detroit, and the city's crumbling infrastructure created a dark and sinister mood as a fitting backdrop for the horrific crimes being investigated. There is suspense, terror, and violence that is often graphic and disturbing.
The mood also well-suited to a horror story, but I think it was a mistake for Beukes to actually move the plot in that direction. The edgy, supernatural elements seemed like confusing "let's stick in some horror" afterthoughts that muddled the story and were just too weird for me. The confusion was compounded by short chapters that switched rapidly and randomly from one character or subplot or point of view to another. I liked the book well enough, but would have preferred a more straightforward and explainable ending to an otherwise compelling story.