Deighton's spy novels are very low-key affairs with muted details that might go by you until pointed out by the protagonist. Often events will occur that seem to have no relevancy until later. To me it seems that not much will happen until the last third, but in retrospect much is happening. It's just that you're forced to see things from the protagonist's viewpoint and that character (like all of us) is in a situation in which he is being forced to act without knowing all the facts. While many might find it frustrating there are times when I enjoy this slower paced approach. It forces me to think a bit more instead of just mindlessly going along for the ride.
"Yesterday's Spy" isn't a bad read. It's set in the mid-seventies (when it was written), but the plot is connected to the French Resistance movement in WWII and how enemies and friends have changed over the past thirty years. The clarity of the war years is gone and that generation is now middle-aged and dealing with a much murkier situation. As a result old loyalties have changed (though there is a possibility that things weren't what they seemed during the war either) and the results won't be as satisfying.
The climax is exciting, but there is also a twist to the slam-bang ending. Once again things aren't what they seem and ultimately the heroes of the past might just turn out to be self-serving bastards who help nobody but themselves.
"Yesterday's Spy" is a satisfying read. Somewhat like a John le Carré novel only not as dense. I breezed through it in a couple of day with most of it being completed within a few hours.