WASHINGTON — (CNN) “Snowden” features a terrific central performance in a slightly better-than-average movie.

And while director Oliver Stone has found material perfectly suited to his conspiratorial interests, he simply didn’t crack the code in seeking to bring this fact-based story to life with the attributes of a thriller.

“Snowden” is still worth seeing, not only for the serious issues Edward Snowden raised about government surveillance and digital eavesdropping, but also Joseph Gordon-Levitt’s disappearance into the title role.

The actor masters not just Snowden’s cadence but seemingly his essence — a slightly nerdy tech genius, ultimately driven to act despite the clear knowledge that in a best-case scenario he’d be forced to become a fugitive from the U.S. government.

Gordon-Levitt is deserving of praise, and possibly more tangible accolades, which the movie as a whole doesn’t merit.

One problem, both for Snowden and the filmmakers, comes in clearly explaining the threat, distilling the technical jargon into something the public/audience can fully grasp.

It’s a point nicely illustrated within the movie when Snowden seeks to school his girlfriend, Lindsay (Shailene Woodley), about the dangers of having the government snoop around in her private digital space even if, as she says, she has nothing to hide.

Unfortunately, Stone’s instincts are often to pound home his points, which here would be better served by a more understated tone.

In that respect, there’s a good compare-and-contrast to be done with “Snowden” and “Sully,” the just-released Clint Eastwood movie that salutes a less-controversial hero.

As with his earlier films, a la “JFK,” Stone goes a bit overboard at times in seeking to lionize Snowden as a patriot — someone whose desire to serve in the military and conservatism ultimately gave way to a more cynical attitude about his government, faced with tangible evidence of its transgressions.

The movie frames this budding realization via flashbacks, with Snowden carefully arranging his first meeting with a trio of journalists — Glenn Greenwald (Zachary Quinto), Ewen MacAskill (Tom Wilkinson) and documentarian Laura Poitras (Melissa Leo) — in a Hong Kong hotel room.

There, he lays out the top-secret information he has accessed, a treasure trove of documents exposing government overreach in the name of thwarting terrorism across two administrations.

In this case, though, scripted drama takes a back seat to nonfiction. Much of this material was covered more urgently in “Citizenfour,” Poitras’ gripping 2014 documentary.

And Stone’s efforts to flesh out Snowden’s personality work fitfully, perhaps least through his relationship with Lindsay.

By contrast, there are fine sequences involving Snowden’s off-the-charts acumen as a self-taught whiz kid, impressing an early instructor (Rhys Ifans) who champions his career.

The movie also captures the discomfort of colleagues within the intelligence apparatus who shared Snowden’s concerns.

The actual making of “Snowden” contained enough intrigue to justify its own documentary.

Yet Stone’s most questionable choice comes at the end, having gone to extraordinary lengths to include footage of Snowden himself, currently living in Russia.

While a fleeting glimpse would have been appropriate — and enough to make one appreciate Gordon-Levitt’s chameleon-like portrayal — the gauzily shot images feel like an over-the-top paean to its subject.

“Terrorism is the excuse,” Snowden says at one point, zeroing in on how fear and the hunger for security have been exploited since September 11, allowing the government to run amok.

While likely to preach to the choir, “Snowden” frames those issues in what is surely a thought-provoking way. But restraint is hardly Stone’s forte, and the director has championed Snowden’s cause in part at the expense of his movie.

“Snowden” opens September 16. It’s rated R.