This novel is so well written that an ugly subject became fascinating. Many characters pepper this book yet even very minor ones were described vividly. The story of a young Bulgarian man's journey from a frightened teenager to a Russian agent during the 1930s and througn WW2 is rich with historical detail and interpretive insight. The use of the Danube river as a connecting "character" adds dimension.
I read this book because I liked Alan Furst's "Night Soldiers" so well. But "Kingdom of Shadows" isn't nearly as good a book. Its scope is narrow and a bit shallow yet seems to want to be broad and meaningful, having the main character, Nicholas Morath, go back & forth between Paris & eastern Europe in 1938/39 on various unofficial philanthropic espionage errands. He gets into dangerous situations and always comes out OK while a beautiful woman patiently waits for him to return to her in Paris. The book does give a glimpse into the underbelly of life in Europe as Hitler invades Czechoslovakia and prepares to invade Poland.