I got this book from the First Reads program (an ARC), and I'll admit that, though it means that I've been living under a rock, I was unfamiliar with this story before I read the book. The author's introduction tries to delineate between this book about Kim Philby and all the others that come before it -- this is the story of a friendship, of his relationship to Elliot -- but in that sense I can't comment on his success. I haven't read all those other books about Kim Philby. So I'll just comment on this one and not place it in the literature of the field.
So this is a book about two men, friends for about 30 years, both spies working for MI6, and one of them is a sociopath. He's also a double agent working for the USSR. But the thing that makes this friendship so interesting is the fact that he's a sociopath -- he was bound to betray everyone he knew because of his obsession with duplicity and secrets, and the USSR seems almost a minor detail. Both of these guys are products of Britain's upper crust. Philby got away with as much as he did for as long as he did (and then got off easy once discovered) mainly because of the profound British belief that rich, well-connected white guys who went to the right schools can do no wrong. That's the theme, over and over. And that's why Elliot can't believe his friend is a double agent.
The author, Macintyre, seems to have great affection for both these men. I can understand that either affection or disdain tends to arise when you spend years researching a couple of people. But he also has great affection for the British system that produced them, applauding that good old boys network when it comes through for them, again and again. He recognizes that both of them, and the people in MI6 in general, have a reverence for the inner circle, the ever-narrowing club resulting from exclusivity, from shutting out the riff-raff, and that led to terrible things. But he also seems to have a bit of it himself. And this is an incredibly British book. You try to use "derring-do" in a sentence with a straight face. Go ahead, try it -- it's not as easy as it sounds. So even as he points out the poison in the system, he seems to have taken a little of it himself.
But we all have our biases. I personally tend toward the other end of the spectrum, toward distrust of the rich and powerful (eh, that's part of what makes me an American commoner). And I saw that arising in myself to protest as I read about these men, described over and over as the best of men. Sure, they both cheated on their women and told packs of lies. Sure, they appointed themselves as puppeteers for commoners, and didn't worry about the consequences. But the author often points out how charming they are, what good friends. How everyone had a good time when they were around, what amazing quantities of alcohol they consumed. Philby, we are told, was a gentle father and a wonderful friend. Except that he was using everyone around him to spy for Russia. I found myself wanting to argue with Macintyre. He has already raised Elliot to hero status, and Philby very nearly so. I found myself suspecting him of some kind of collusion.
So I had a complicated relationship with both the subjects and the author during my read. But it was definitely a good read, one worth recommending to folks interested in the cold war and spying in general. Especially being British and rich. It was a very well-told story, with, as I say, much affection. I'll recommend it highly and leave it to other readers whether they share in that affection.