"Blood Of Victory" by Alan Furst. Not my favorite Furst novel, but the one I decided to reread. I'm sticking with it because he is fantastic at creating an atmosphere. Every hotel, nightclub, and train car seems authentic.
It's set in 1939. Britain is holding on by a thread, and the Nazis are enjoying life in Paris. A Russian writer has resident alien status in France, and is being recruited by various governments to act as an agent. "Oh, you met her? She'd recruit God."