... I thought this was one of the best Spenser novels at the time of its publication, but I do recommend reading it in sequence. Especially, read "A Savage Place" first, because the two books have a certain relation to each other.
This is a bit more of a mystery than others in the series in that you don't discover the murderer's identity until the end, and this is good in adding a bit more suspense than usual.
Spenser's hired to protect a very obnoxius TV star, who's addicted to drugs, alcoholic, arrogant...listed alphabetically, I'd be naming several other character defects before we get to nympho, and that's just past the middle of the alphabet!!! On top of all this, she might be making up all these threats she's supposedly receiving. However, when her double is murdered, Spenser has to take the task of protecting her more seriously. He has a hang-up about protecting women since an unpleasant happening earlier in the series.
I had a suspicion around half way through as to who the murderer was...I won't tell you whether I was right or wrong. However, I believe the suspicion was deliberately & subtly planted by Parker, and if so, I admire him for the way he did it. Like I say, I'll let you find out whether this was deliberate foreshadowing for dramatic effect, or a red herring to distract you.
I do recommend this highly, but if you're not already a Spenser fan, read several earlier books including "The Savage Place" first in order to better appreciate this.