Sadly enough this will be one of the last Bernie Gunters because Philip Kerr, who was suffering from cancer, sadly passed away recently, only aged 62. https://www.theguardian.com/books/2018/mar/25/philip-kerr-obituary

Prussian Blue starts in 1956 in France. Bernie is kidnapped by Stasi thugs, one of them a former colleague who was with him on a case in 1939. This brings the story back to 1939, to Berchtesgaden, Hitlers retreat on the Obersalzberg. Both stories alternate in the book with the emphasis on the 1939 story, which makes for interesting reading about the corruption among the top nazis. I'm sure it has been well-researched by Philip Kerr who always blends in real-life persons with fictional characters. It is fun to Google some of the characters, just to see what they looked like in real life and to read a bit more about their backgrounds and lives on Wikipedia.

This is a true Bernie Gunther, wisecracking and getting himself in all kinds of trouble while solving a crime. Highly recommended. The first three will always be my favourites but the rest of the series is also of a high standard.