After the brilliant (and Edgar-winning) one-two punch of Fletch, and Confess, Fletch, Gregory Mcdonald's mystery novels got progressively worse. I still read them because of the wit and the prose-style but the books became vehicles for Mcdonald to spout off on whatever political clap-trap was rattling around in his brain. This book (it's readable, well, I read it) is pretty insufferable, with each of the small-scale mysteries that Inspector Flynn of Boston solves just there so Mcdonald can make a point.
John D. MacDonald occasionally did this as well (inserts his opinions) but he never forgot that the most important thing about the book is the story and characters. They should always come first.