Audio.
Historical mystery, but recent history.
Nate Heller is a Chicago PI that gets pulled into a story of paranoia and paranormal (Red Scare and Roswell) and interacts with the likes of James Forrestal, Harry Truman and a number of others. Our hero survives and thinks he's discovered the real secret of Roswell by the end.
There was something a little modern about the story telling, though. I can't put my finger on it. It tried to be hard boiled, but ended up being flip instead at times.
Still, I enjoyed it. Apparently the tenth book in a series that includes in its mysteries finding out what happened to Amelia Earheart, hanging with the Chicago Mob and interacting with Frank Sinatra. Could be interesting.