I'm about halfway through
The Arms Maker of Berlin 
and finding it getting better.
It's two novels in one: A present day hunt for secret archival materials; and a backstory set in WWII-era Germany that takes up half of the story. The back-and-forth can be good or bad depending on your reading tastes. It's working for me just well enough, though who's really the antagonist is a little murky (not a bad thing necessarily). I'd call this an intelligent thriller about uncovering the past.
Happy New Year!
Steve