I agree with those that feel that the Spenser series has seen its best days. Maybe Parker realizes that also, and is using the dog Pearl's aging as a plot device hinting that time is catching up with all the characters. Yeah, Spenser must be about 70...Hawk too, and Susan not far behind. Quirk and Belsen must be ready to retire from the police department, and is that a transistor radio Vinnie Morris is always listening to, or a hearing aid?
Still this isn't a bad book and spending two or three hours with it is more enjoyable than most of what you'll find on TV.
Maybe some of Spenser's readers are tiring also. I saw a couple of reviews written by those who seemed to have lost out on who killed Nathan, and others who didn't see the significance of Susan's client who commits suicide compared to the possibility of Nathan's suicide, or her feeling of failure because of her client's suicide compared to Spenser's failure to protect a character who came to him for protection. All of the above shows that Parker hasn't lost it yet, but I fear he's tiring.
This Spenser book does have a surplus of characters, even after a larger than usual number of them get killed.
So what am I saying? I'm saying that this is a must for Spenser addicts, but only because it is Spenser. However, it is rather pedestrian and it may be that your strongest emotion in reading the book is regret that Pearl is indeed getting pretty old.