The Innocent takes place in West Berlin during the Cold War, prior to the construction of the Berlin Wall. Much like other McEwan novels there is an element of fact that makes his historical fiction seem more realistic. In this case, protagonist Leonard Marnham is an engineer secured by British Intelligence to work with the joint CIA-MI6 forces on Operation Gold, a real project that focused on tapping KGB phone lines underground - you can read about that here.
But while the realism is present in the history, some of the fictional characters tossed in seem little more than stereotypes. Leonard, whose character arc is certainly the largest, begins as a stereotypical uptight British male who is initially offended by Bob Glass's even more stereotypical American mindset, though Leonard eventually adapts to certain Americanizations. Glass's character is framed by the two Americans Leonard spots from the car on his first visit to the warehouse, tossing a football back and forth, who generate more stereotypical thinking on Leonard's part. Glass remains pretty consistent for most of it. Even his deus-ex-machinesque actions towards the end are somewhat American-comic-book-hero-ish.
While Leonard's stick-figure-ness may be an error of judgement on McEwan's part, the Americans seem to be drawn as such on purpose. About three-quarters of the way through the book, Leonard observes this innocent American quality in the things around him:
They think of everything, he thought, the Americans. They wanted to make things possible, and easy. They wanted to look after you. This pleasant lightweight staircase with the nonslip treads and chain-link banisters, the Coke machines in the corridors, steak and chocolate milk in the canteen. He had seen grown men drinking chocolate milk.More stylistic in character is Maria, the german divorcee with whom Leonard finds himself in love. Her approach to life is markedly refreshing and allows Leonard to grow out of his pre-constructed shell, into something a little more interesting, a little more daring, and certainly more dangerous.
Generally, with McEwan, there's a naturalistic vein that pulses throughout the narrative and hemorrhages at the climax,spending the rest of the novel trying to repair itself. In Enduring Love, the break comes early, muddling the facts and confusing the main character for most of what follows. In Atonement, it's a continuous, hemophiliac flow that breaks like a cold sweat and a chill at the end. Here, though, McEwan is a bit more economical and somewhat more Shakespearean in his formula - you could almost mark out the five acts with their building, subsiding and ultimate third act climax.
While the formula works, it's a little slow-going; it becomes weighed down by the author trying to inseminate it (sorry) with as many sexual innuendos and metaphors as possible, seemingly in an attempt to get his point across - defying any assertion that anyone is completely innocent. Perhaps in 1990 (just after the fall of the Berlin wall, when land lines were the rule and were easily enough tapped, when DNA evidence was still a new thing, before the internet could tell everyone's secrets), this was a more poignant story, but today its historical relativism isn't very significant and only the baser details* remain truly relevant.
*Spoilers (if you've not read the book, you may want to skip this part):
If you've read the novel, you'll understand why this is relative - my mother just now informed
me that the police have found the body of a Bronx man stuffed into a large duffle bag this
weekend. I guess people still do that kind of thing.