Shaneystar2, I am on the 7th one in the series and still enjoying them. The one I found quite a bit of a difficult read was the 3rd one, Kaleidoscope. I read some reviews on GoodReads and they seemed to echo my own thoughts.
If you are interested in that particular period (as I am) you may like Alan Furst's books, if you haven't already tried them. They aren't police procedurals but he's my favourite author for that prewar European period.