PARK CITY - The documentary that styles itself as a genre film is a risky gambit -- for every example that pulls off the disguise (think Bart Layton's elegantly shifty "The Imposter"), there's at least one other that carries a faint whiff of desperation, employing thriller tactics in the hope of sexing up serious-minded material, selling its subject and audience short in one fell swoop.

Early on in Nadav Schirman's "The Green Prince," a smart, tightly assembled film that kicked off the World Documentary Competition at the Sundance Film Festival tonight, there's reason to fear the film will fall into the latter camp, as title cards skitter across the screen in that analog typeface native to the contemporary Hollywood war movie, as an ominous, militaristic score rumbles in the background. "Yes, here's another urgent reflection on Israeli-Palestinian politics," these embellishments appear to say. "But wait, this one's exciting."

To be fair, you can see why a film on that subject feels compelled to distinguish itself by any means necessary. In 2012, "The Gatekeepers" exhaustively tackled the subject of Israel's Shin Bet security service, while last year yielded not one but two narrative studies -- one from Israel, one from Palestine -- of young Palestinian informants entangled with the organization. (The Palestinian effort, "Omar," was nominated for an Oscar this morning.) "The Green Prince" enjoys a degree of overlap with all these films, yet its tonal approach is distinct, at least in part due to its stylistic affectations. And to be doubly fair, the whiz-bang window-dressing is just that: you needn't look too hard for a moving personal account to emerge from beneath the movie-movie subterfuge.

The source material might easily have made for a narrative film; indedd, it may yet do so. Former Shin Bet ally Mosab Hassan Yousef's autobiography "Son of Hamas" was published in 2010 and became something of a hot news item, serving as it did as evidence in Yousef's legal battle for political asylum in the US. He wrote it, he says, because he was struggling to get Americans to believe his story at all.

Certainly, it's a remarkable one: the son of Sheikh Hassan Yousef, founder of the Palestinian resistance movement Hamas, Youself was cornered at just 17 years of age into becoming Shin Bet's most valued and well-connected informant. For over a decade, he provided first-hand information on his father's group that led to the prevention of numerous bombings and the identification of terrorist leaders. ("The Green Prince," of course, was his codename to his Shin Bet handlers.) The cruel kicker: his cover was so watertight he found it impossible to prove he wasn't affiliated with Hamas activities.

This is engrossing, even hair-raising stuff, though in packaging it as a taut political thriller -- complete with shadowy re-enactments and sinister drone footage -- Schirman perhaps doesn't best serve the more searching story of personal transformation at hand here. As a bristly teenager, Yousef enters dealings with Shin Bet with the intention of acting as a double agent, laying the foundation for revenge on the Israelis, but undergoes a radical flip-flop in political allegiance as he's disillusioned by findings of torture and abuse committed by Hamas. (His lingering childhood trauma from a sexual assault also plays a role.) His rejection of his father's people principles extends as far as conversion to Christianity.

This self-identification process is initiated and enabled by Yousef's close relationship with his chief Shin Bet handler, Gonen Ben Yitzhak, though the strength and significance of their friendship becomes entirely clear only in the film's sweetened final reel. Until then, their testimonies are shot separately, sometimes snippily intercut, in a crisp, atmospherically lit talking-head style that doesn't allow for much intimacy.

The slower reveal and chilly formality are effective, indicating just how hard-won any form of trust is in this fraught business, though it doesn't present the film's human subjects in the most nuanced light -- avuncular and articulate, Yitzhak remains predominantly a closed book on camera, his proven actions speaking more to his kindness and defiance than his words.

Perhaps because he's revisiting experience he's already written about, meanwhile, Yousef is a generous but mannered interviewee, with a taste for literate turns of phrase that don't sound entirely spontaneous -- he alludes at one point to his fight "against a most dangerous enemy: the force of shame." Spontaneity may be one of the first things to go out the window in a life lived so heavily in secret; as a result, "The Green Prince's" genre contrivances began to feel oddly apt to a study of a man who has acted to survive since he was 17. Polished, propulsive and affecting even when it doesn't let down its guard, Schirman's film points to the rich multitude of complex personal stories yet to emerge from this open wound of a conflict.

Guy Lodge is a South African-born critic and sometime screenwriter. In addition to his work at In Contention, he is a freelance contributor to Variety, Time Out, Empire and The Guardian. He lives well beyond his means in London.