Call for the Dead - John le Carré
All of Le Carre's signature skills, insights and character development techniques are found in this initial effort. The author's supplemental introduction is most valuable for someone just getting into his immense body of work.
He's a master of this genre, and thankfully is still producing. He adapts well with the changing world, but even so, a read of his Cold War titles always seems "current," as history has a way of repeating itself.