Killer by Jonathan Kellerman

Child psychologist Alex Delaware is offered what looks like an easy case in a child custody dispute between two sisters, with one saying the other is not a fit mother.  Of course being a mystery novel nothing is ever simple.

Dr. Delaware has his life threatened, there is a murder, and Milo Sturgis, friend and LAPD detective becomes involved. 

Medium paced novel that gets the reader to think, always a positive.  The ending is interesting as all of Kellerman's books tend to be and leaves you wanting just a few more pages. 

Part of a series but the books do not have to be read in order.