Shiver by Lisa Jackson (2007, Paperback, Reprint)

In this book, Detective Ruben Montoya is back investigating two murders....one of a of a local shock D.J. and there other of a female college student who was to become a novice nun. Montoya is still grieving the loss of his lover Marta, so he is not to keen to jump back on a case, especially where the prime suspect is the D.J.'s wife, Abby Chastain.
As victims start to pile up, it has become more than obvious that Montoya is dealing with a serial killer. All the clues point to Our Lady of Virtues convent, a local mental hospital, where decades ago, Abby's mother fell to her death. Adding to the mystery of the whole scenario is that each victim was the complete opposite of the other. Montoya does not believe that Abby is the serial killer, but somehow she is tied in with the murders, but why?

Ms.Jackson will keep you guessing until the end on the killers identity. It was somewhat of a slight disappointment to find out who actually killed everyone. Maybe that is what makes a story good. The unexpected.