This is a somewhat dated book, having been published in 1968, but that doesn't diminish its reading quality. It is devoid of the slick gadgets found in so many spy novels, probably because the primary characters are not spies themselves, and this makes it a much more believable narrative. Mathison, a lawyer who is also the main character of the novel--he is the main character, despite his relatively late appearance--is just trying to figure out what he's gotten himself into and help someone out. He doesn't want to be a spy, and he doesn't really engage in that much spy-like activity. That's all left to other characters, making Mathison extremely engaging. Because we experience the story mostly through his perspective, we get the real experience of what he's going through, rather than jumping right into the shocking doings of the underworld.
MacInnes also has a wonderful layering effect going on throughout the novel. As said before, there are a lot of moving parts, and just when you think you have all of their paths figured out, she adds another dimension--some of which aren't revealed until the very end. They aren't huge twists that will completely change the plot for you, but they do add a lot of "oomph" to the experience and make it seem a much more "full" narrative. I didn't really buy into the romance subplot, because I felt it wasn't worked enough to be really engaging, but that wasn't the main point of the book so I can let it go. Overall, I would definitely recommend this to anyone who likes spy stories, mysteries, Nazis, or novels about the complicated relations of the cold war.
4 out of 5 stars.