Read "Black Mirror"

I needed a fast mystery, and someone pushed “Black Mirror” by Nancy Werlin in front of me.
Frances Leventhal’s older brother Daniel dies from a massive heroin overdose. His only note was for his girlfriend, Saskia. Trying to work through her grief, she decides to join Unity, a charitable organization that Daniel had belonged to and was almost fanatical about. But she is informed that she is not welcome, and she becomes curious. It seems that there is something strange about the group and she realizes certain things that she never has before….
Werlin writes very good books. “Mirror” was suspenseful and a quick read. Even a little scary. I recommend it highly. Have any of you read it?