Michael Frayn is a very good writer, and it's probably fair to say he's rather undervalued in the United States, insofar as he's known at all. But his timing with Spies is seriously unlucky, and the novel's publication is therefore unlikely to improve his fortunes. Although it's a skilfully made piece of work, it has arrived more or less contemporaneously with Ian McEwan's Atonement (reviewed in Slate by Geraldine Brooks and me a mere fortnight ago), and this coincidence will inevitably obscure its merits; the two books have a great deal in common, and it's unlikely many readers will opt to read them both.
Both play out against the backdrop of the Second World War, both take place in the English countryside. Both implicitly evoke conflicts based on class distinctions. Both involve false (and arguably malicious) accusations made by over-imaginative pre-pubescents inspired by their spying upon, and misinterpreting, the clandestine adult sexual doings occurring in their midst. And both novels examine the lifelong guilt that ensues when these fantasy-inspired accusations have tragic real-life consequences.
Now, Spies is too good to be facilely dismissed as the lesser book, but it is, I think, the slighter. I don't wish to belabor this comparison, the tendency of which may be invidious, but while Atonement is a grand panorama, Spies is, as you suggest, a claustrophobic, brooding miniature. And it's possibly, as you also suggest, a little longer than it needs to be, considering the constricted scope of its action and its relative dearth of incident. Given the choice, most readers would probably opt to read the former. And I don't think they would be wrong to do so.
But still, Spies boasts many strengths. Not least is the way it sustains its extraordinarily oppressive, anxious atmosphere. This is a very suspenseful book, and one reads it with a growing sense of dread, expecting, on almost every page, the very worst to happen. This is no small achievement, especially considering how low the fictional stakes are, how trivial "the very worst" actually is. All that's at risk, or at least appears to be at risk, is minor social embarrassment, and yet I constantly found myself almost writhing in appalled expectation of what was going to happen next. To cite anything comparably unsettling, one would have to turn to the horror genre, to something by Stephen King or Peter Straub, say.
And Keith is a superb creation. Surely one of the most unpleasant children to be found in English literature, he is nevertheless also a fully realized and credible character, haughty and supercilious certainly, impatient, imperious, and intolerant; but also friendless, dyslexic, socially inept, and a pathetic, docile victim of parental abuse. It isn't difficult to understand the power he wields over Stephen (or, more accurately, the power Stephen invests in him); it is all too easy to recognize the ways in which he has begun to resemble his coolly sadistic father. And the Oedipal ramifications of both his situation and the events he sets in train are adumbrated by Frayn with a very deft touch indeed. Keith thinks he is accusing his mother of espionage, but he is in fact accusing her of sexuality. That for him is the real, and the unforgivable, betrayal. And it is a crime of which she is guilty.
And notice how acute Frayn can be on class differences, and even more penetratingly, on the insidious way class differences are internalized early in life:
…[N]ow I can see the colours of our belts. Keith's, also fastened with a metal snake curled into the shape of an S, has two yellow bands on the black background, mine has two green bands. We're socially colour-coded for ease of reference. Yellow and black are the colours of the right local preparatory school, where all the boys are going to take, and pass, the Common Entrance exam to a public school, and where everyone has his own cricket bat, his own boots and pads, and a special long bag to put them in. Green and black are the colours of the wrong school, where half the boys are gangling oafs like my brother Geoff, who have already taken Common Entrance and failed, and where we play cricket with splintered communal bats—some of us wearing brown gym-shoes and our ordinary grey shorts. … Not just his belt but everything about him was yellow-and-black; everything about me was plainly green-and-black. He was the officer corps in our two-man army. I was the Other Ranks—and grateful to be so.
Where we disagree, you and I, and disagree completely, is on the denouement. This is a chasm between us that can't be bridged. You say the plot "is resolved in an immensely dramatic and satisfying fashion." I can only shake my head in wonderment. I found the book's climax to be deeply undramatic, clunky and amateurish and perfunctory. Virtually every element in it that might have qualified as a surprise has been telegraphed for most of the book's length. Were you really surprised to discover that Stephen is Jewish, for example? The fact is actually revealed on Page 81 (which is the only reason I feel no compunction about revealing it here); this goes beyond mere foreshadowing, this is giving the game away outright. Were you in any doubt as to the identity of the mysterious stranger (and this time I shall not say more, although I suspect my scruples are supererogatory)? That identity was clear to me, based solely on basic story-telling principles, for well over a hundred pages before Frayn got around to unveiling it. And the pathetic secret of this mysterious stranger … well, it seems to come out of another novel (by Pat Barker, perhaps) and to beg a completely different set of questions from the ones raised by the book we've been reading. And in addition, with all the tensions ratcheted up so efficiently over the course of the book—and despite the single note of tragedy, played in rather muted fashion—things just sort of peter out at the end.
Anton Chekhov would have taken Michael Frayn to task for introducing a loaded gun in Act I and then failing to fire it in Act III. In fact, Frayn introduces quite a number of guns in Act I, and almost all of them prove to be loaded with blanks. (The only one that isn't is a knife. But it would be wrong to say more about that, beyond mentioning that it's the sort of stunning scene, with an even more potent aftershock, that is otherwise absent at the book's climax.)
Or perhaps you think I'm missing something?