Susan,
It does sound like a turn or change for the series (and I am a fan - didn't like what Disney did with Murder, She Meowed aka Murder, She Purred - book was much better). I'm behind in the series, haven't read maybe the last couple including the one you are talking about. I'm sure Rita Mae probably is no stranger to soap boxes, they usually aren't a part of the mystery series though. I also like her Sister Jane Arnold series featuring Foxhounds and a hunt club. IF I were only going to recommend one out of the Mrs. Murphy series, it'd have to be
Muder At Monticello. The books really capture Virginia culture/nuances - natives at least.
In the dog related mystery series around, I also really enjoy Susan Conant's Holly Winters series (Alaskan Malamutes) and Melissa Berenson's Melody Travis (Standard Poodles) series. Both have corgi mentions in at least one of the books. Carole Lea Benjamin's mystery series is a lot of fun too and I've read several of those, just a little harder to come across in my area.
Debbie