I haven't read a Robert B. Parker book in a while, and I'd forgotten what a master of engagement he is. His books go down so smoothly, each chapter leaving you hungry for more. How? Why?
Part of it is just the magic that some writers have. Parker's style is simultaneously spare and full of apparently insignificant details; the effect is to immerse the reader without effort in a very real-seeming world. The impetus of the plot is internally generated, creating an organic sensation of forward momentum that all the careful study of plot structure in the world can't convey.
In other words, even late in his career the old master still had "it," whatever "it" is. "Sea Change" is almost stunningly more readable than most of what's out there.
At the same time, I can't say that it's Parker's best work. If you've read his other works, you'll recognize a lot of the same setup: an undefined relationship that requires a lot of therapy sessions for the main character to understand, set against a backdrop of a sordid story of sexual exploitation and abuse. And what is this with the fake accusations of rape? Kudos to Parker for making an effort throughout his career to write interesting and sympathetic female characters, but he never could quite shake the sexualization of his women, all of whom are more or less sex-mad.
That being said, "Sea Change" is a high-quality prose treat. If you're a Parker fan, you'll probably enjoy it. If you haven't read any Parker yet, you might want to start at the beginning of the series, but this will also give you a good enough intro. Either way, you're likely to enjoy it.