Maybe it’s better late then never.

Science fiction writer Philip K. Dick never really found fame in his life. The writer’s body of dystopian novels and short stories gained him a devoted cult following before his death in 1982, but little more. But ever since “Blade Runner,” directors have found his art to be a goldmine for film adaptations. His mind-bending science fiction makes for good eye candy and his acute sense of undercurrents in the world around him allowed him to touch on the fears and anxieties of a techno culture that was only just beginning to emerge in his lifetime. At times, he seems prophetic.

The adaptations of Dick’s works have ranged from the good (“Minority Report,” “Blade Runner”) to the bad (“Paycheck”) to the just plain silly (“Total Recall”).

“A Scanner Darkly,” Richard Linklater’s adaptation of the 1977 Dick novel of the same name, thankfully is one of the former and maybe the finest Dick adaptation to date. It’s certainly the most prescient, raising questions of personal freedom and government power that mean more now than ever.

The film is set seven years in the future, and follows the life of Bob Arctor (Keanu Reeves), an undercover government agent trying to stop the menace of Substance D, a new pill that might be the most addictive drug yet to hit the market. Like the other agents he works with, Arctor wears a high-tech suit on the job, displaying a constantly changing collage of people parts that makes him impossible to recognize, even to other agents.

But Arctor plays another role: a Substance D user and dealer. He lives in a rundown Anaheim house with two other addicts, the dopey Ernie Luckman (Woody Harrelson) and the devious James Barris (Robert Downey Jr.). They are periodically joined by Arctor’s girlfriend, Donna (Winona Ryder), an addict who refuses to have sex with her boyfriend.

Their actions certainly don’t say much on behalf of the drug, as they walk through the movie paranoid and confused. At one point, Barris buys a

bike for $50 that he was told has 18 speeds. But when Luckman notices there are only three gears on front and six in the back, the group launches an elaborate conspiracy theory about where the other 10 gears have gone.

Not all of the group’s conspiracy theorizing is without warrant. When Barris comes to the police to rat out his friends, Arctor has to sit in his suit listening to the allegations against him. After Barris leaves, Arctor’s chief orders him to start surveilling his own life.

It would be bad enough if this was the worst way Arctor has been pitted against himself, but the Substance D habit also begins to take its toll, turning the left and the right hemispheres of his brain against each other. What’s real? What isn’t? Even at the end of the movie, following the usual Dick assortment of plot twists and turns, it’s hard to tell.

“A Scanner Darkly,” like Linklater’s earlier film “Waking Life,” uses rotoscoping technology. Each frame is filmed using real actors but with animation added on top of the film. The effect is trippy, and thus fits the film’s theme. It’s not hard to imagine other directors being inspired to use the technique for purposes of mere eye candy, but Linklater’s stroke of genius is using it in a way that adds to his films.

Linklater’s time spent directing mainstream films (“School of Rock” and “Bad News Bears”) seems to have helped him. His films always have been smart, but maybe too smart for their own good, going off on monotonous intellectual tangents. In “A Scanner Darkly,” he keeps the pacing tight, and the pontificating never interferes with the action, only drives it.

Linklater also makes good use of Reeves. Reeves always has been a limited actor, but he can be gold when cast properly. As long as he’s playing a confused dystopian wanderer, he’s believable. Downey and Harrelson have some priceless moments to provide levity to the dark story. Ryder is also great in her role, which starts out minor but becomes the emotional crux of the tale by the end.

For all the none-too-thinly-veiled commentary on drug use, free speech and personal privacy, the film works so well because the people seem believable in this era of the Patriot Act.

Even if the government’s methods are questionable in the film, it’s hard to defend the use of Substance D considering the addicts’ behavior. Yet it’s equally hard to vilify the addicts when it becomes clear that they’re just normal people, confused and victimized by their own habits and the government trying to protect them.

No one in “A Scanner Darkly” is truly good or truly bad. And each character can appear well intentioned and right from their own perspectives.