I have read every book in the series. The last 3 or 4 have had much less interaction with the peripheral characters. In fact we've barely seen some of them.
It begins to feel like the exercise is about cranking out another novel rather than spending the time and effort on the characters.
This story didn't flow into the solution to the murders. The solution just seemed to appear without the usual methodical development.
After so many in the series this was a disappointment.