Prussian Blue by Philip Kerr

Prussian Blue continues the always enjoyable and enlightening journey of Bernie Gunther, former Berlin cop and Nazi hater when that philosophy wasn't too popular in the Homeland.  Prussian is divided into two intertwined stories--one set in 1939 at Hitler's mountain hideout, Berchtesgaden, where Bernie (the cop) is called in to investigate the murder of a civil engineer just before Hitler himself is due to arrive for a big birthday celebration. The other plot is set in 1956, when Bernie is ordered by the East German state police (the Stasi) to kill a woman who had played a major role in a previous Stasi operation. But Bernie knows that once she's dead, he will be the last one left who knows about the previous operation, so someone will be out to kill him too. Despite its considerable length (over 500 pages), the book moves at a pretty rapid clip as Bernie is trying to find a killer in a week in 1939 and trying to escape the Stasi agents in 1956. Once again, I can't wait to see what happens next.

If you're new to this excellent series, start at the beginning with March Violets.