Apparently the protagonist in this book (Carolyn Sullivan) has figured in a series of NT's books? Not clear, but the jacket implies that. 
 In any case, Carolyn's best buddy and fellow probation person is murdered, and then Carolyn's buddy's husband is murdered, and then Carolyn nearly murders the one she thinks is the murderer - oh, and the dead husband was accused of molesting his and Carolyn's wretched teenage daughter, who is a totally disgusting person and Carolyn has a boatload of Catholic guilt so when this disgusting junkie ho is tossed out by her Dad (before he gets it) Carolyn takes her in, but of course the little skank steals money and a car and an iPod (onto which a year's worth of downloads were lovingly installed by Carolyn's child, who is pretty much ignored as Carolyn goes around solving the crime(s)). 
 What made me nuts is that about every half a chapter or so, one of the people in the PD and/or the probation dept. would summarize the chronology of who killed whom and why, and it was just too much of a device to keep us guessing. I wanted to just say "yeah whatever" and get on with my reading and not have to wade thru ANOTHER detailed theory. 
 but what do I know? About halfway thru, I was thinking it was Carolyn's fiancee...and what about the red herring of her daughter's new boyfriend, who used to play football? Am I the only one who kept waiting for it to come out that she had hooked up with the refugee from N'Awlins? 
 Anyway, it was a quick read, kept my interest, glad I didn't buy it, and now on to the next diversion...