Recently, I discovered the spy novels by Alan Furst. Beginning in 1988, and continuing through 2010, he has written eleven novels in the series dubbed the Night Soldier Novels.
So far, I have read the most recent six of the eleven and in addition to being entertained, I have learned quite a bit about events leading up to World War II and particularly the geography of Europe, including eastern Europe.
I particularly liked the most recent book in the series: Spies of the Balkans.
But Costa Zannis must deal with them all. And he is soon in the game, securing an escape route-from Berlin to Salonika , and then to a tenuous safety in Turkey , a route protected by German lawyers, Balkan detectives, and Hungarian gangsters. And hunted by the Gestapo.
Zannis travels throughout central Europe and I was able to follow those travels on the prefatorial map. Doing so solidified my understanding of the geographic relationships of Greece, Germany, Austria, Bulgaria, Romania, Hungary, Yugoslavia, and Czechoslovakia (in the case of the last two, remember this is pre-WWII Europe).
In the other novels I have read, his main characters are located in, or travel to or through, France, Spain, Portugal, Denmark, Poland, and Finland. They even appear in Egypt and other north African countries.
You can be sure I am going back and reading his earlier novels as well.