I am not sure why this one got recommeneded to me but The Spy and the Traitor as been on my list for a while now. I am happy to have watched The Americans before reading it because there was quite a lot of crossover.
The story of Oleg Gordievsky is a fascinating one that I did not really know in any great detail. I did know a bit more about Aldrich Ames, but this story was less about him per se than how he fit into Oleg's story.
True stories are often more unbelievable than fiction and some parts of this story fit that description. I found the whole thing to be exciting even though I had an inkling of how it was going to turn out. If you do not know the story then I highly recommened reading this book before doing any more digging.