They get worse and then get better. My daughter loved Arms and the Women, but I didn't like it much. I strongly disliked Death's Jest-Book and Dialogues of the Dead, but I enjoyed the more recent Death Comes for the Fat Man and Cure for All Diseases (I don't know why in Canada we had the UK title for one of these and the US title for the other ...)

Editing: It gets weird late in the series - about where you started, or maybe the few before that are of uneven quality. The early ones are great classic British police fiction. Like Wexford.

Do you know Robert Barnard?