Realistic spy fiction is hard. On screen, it's almost never done. The tendency to romanticize espionage is so ingrained in us through decades of James Bond and Bourne and 24 that a warts-and-all depiction of the way intelligence agencies actually operate might not even make sense to much of the moviegoing public. Occasionally, someone will make a minor, based-on-a-true-story attempt – The Good Shepherd with the CIA, for example, or Breach with the FBI – but those are viewed as history lessons, not spy thrillers.

That makes sense. The CIA doesn't exactly have an open-door policy, so it's hard to say for sure, but by all accounts the work of a real-life agent isn't terribly dramatic, or ripe for genre film treatment. Much of it is a bureaucratic nightmare, and the jobs that we view as exotic and exciting – "secret agent," for example – are usually a tedious slog, consisting of years of building connections and forging allies in the hopes of a payoff in the indefinite future. Yeah: all else equal, I'd rather watch Jason Bourne kick some bad guys in the face while searching for his true identity.

David Ignatius, novelist and long-time foreign affairs columnist for the Washington Post, knows this well. With Body of Lies, currently being adapted by Ridley Scott and William Monahan, he tries a compromise: a thriller that keeps a plausibly realistic view of the CIA and looks elsewhere for drama. Specifically, Ignatius sticks with a gritty, convoluted, technical spy plot and supplements it with a treacly, sentimental, sometimes steamy romantic subplot that eventually collides with the A-story, culminating in a conventionally heartwrenching damsel-in-distress climax. The CIA may be boring, but that'll get their attention.

The novel's romance between intrepid CIA agent Roger Ferris and saintly humanitarian aid worker Alice Melville is so impossibly earnest, so sappy, that it cannot possibly make it to the screen unaltered – at least not if ultra-smart screenwriter William Monahan (Kingdom of Heaven, The Departed) has anything to say about it. And indeed, it's not even clear that Alice will be in the film, which is in post-production for an October release: the IMDb doesn't have an entry for the character, and there's been no casting news regarding her. By contrast, Roger's seductive, manipulative wife Gretchen is present and accounted for, to be played by Black Book's Carice Van Houten despite the role having been tailor-made for Angelina Jolie. Possibly Monahan decided to merge the characters (which would eliminate a nifty mid-novel interlude where Ferris faces a legal investigation thanks to Gretchen's blackmail), but if Alice has indeed been excised altogether, then the ending will have to be radically reworked.

The main plot concerns an ingenious plan by Ferris (Leonardo DiCaprio) and his CIA boss Ed Hoffman (Russell Crowe, rather than a stocky man in his late 50s as Ignatius wrote the character) to stymie a network of al Qaeda car bombers by making it appear as if the CIA has infiltrated it. (Hint: the title is a pun of sorts.) Until all hell breaks loose in the aforementioned climax, there's precious little in the way of action: the story moves forward via conversations, debates, the leveraging of resources and contacts. It's fascinating stuff if, like me, you enjoy process, but it's not terribly cinematic. Monahan showed a flair for this sort of thing with the cat-and-mouse elements of The Departed, but it will take some deft handling, not least because the characters' shadowy maneuverings get confusing even as they sit on the page, to say nothing of what could happen when they whiz by on the screen.

There's a twist ending I won't discuss, except to say that if the film pulls it off, it will earn itself some repeat viewings this fall. Ignatius does a nice job of telegraphing the revelation just enough that while it isn't quite guessable, it seems perfectly logical when you rewind the plot in your head. It's a tricky balance.

Politically, in case you're wondering, the story is pretty neutral, at least as Ignatius has it: terrorists are bad, the people trying to stop the terrorists are good, non-extremist Muslims are decent folk. It doesn't even glorify the CIA, which at the end of the day winds up looking pretty ineffectual. Ridley Scott was reportedly denied permission to shoot the film in the United Arab Emirates for political reasons (he went to Morocco instead), but there's nothing searing here.

Body of Lies, the novel, is pitched as a spy thriller informed by the author's extensive experience in the field and knowledge of the way the CIA really operates. (The back cover offers a fawning quote from former CIA director George Tenet, claiming that the book is "fiction but reads like fact.") It's certainly intelligent, plausible, and sometimes exciting. That Ignatius felt the need to pull his punch by throwing in a love story straight out of a Hollywood movie is understandable – as I say, the work of the CIA isn't always high drama – but regrettable. If Scott and Monahan can tighten Ignatius' plotting, the movie could become the genre's high-water mark.

Next week: A look back at Sean Penn's interpretation of Into the Wild by Jon Krakauer.