Although it doesn't say it anywhere on/in the book, this is a sequel to 'Silk.' I've already read Silk, so that was convenient. However, this works perfectly well as a stand-alone novel. The events of the past are a significant, driving force to the plot, but they're explained, as necessary, as the book moves forward. The overall feeling is like that of real life, when one meets a person and significant events have already occurred in their lives. Fiction often fails to convey that; this succeeds.
I wouldn't say the book is completely successful, however. The setup is good - Niki is a disturbed, seemingly schizophrenic woman, taken care of by her frequently absent, rock star wife, Daria, who has her own problems. Niki cannot get past the horrific, supernatural events of ten years prior, and isn't sure if they are the product of her mental illness or not. As this is a supernatural horror novel, it's not much of a spoiler to say "they're not."
However, I felt that the fantasy world that ends up figuring in the plot wasn't as sharply drawn as it could have been, and the big showdown lacks the dramatic tension it had the potential for.
Still, I do like this writer.