There’s a bit of a passionate Internet fan community that’s grown up around the film “Mr. Nobody.” That’s is a bit odd when you consider that the mind-bending and eye-popping sci-fi-flavored fantasy doesn’t open until this weekend.

Yes, I know: The movie, the English-language debut of Belgian filmmaker Jaco Van Dormael (“Toto the Hero”) was technically released in 2009. But ever since its premiere at the Venice Film Festival that year, it has never found a U.S. distributor, until now. (The movie is opening simultaneously in theaters and on-demand.) Despite the four-year delay, word of the film has spread among cineastes, thanks to other festival screenings and the film’s availability on imported DVDs.

Surprise — it’s quite good.

Jared Leto stars as the 35-year-old incarnation of the title character, Nemo Nobody (“nemo” means “nobody” in Latin), whom we also meet at various other life stages: age 9, played by Thomas Byrne; age 15, played by Tony Regbo; and on Nemo’s 118th birthday, when he’s portrayed by Leto under a pound of pretty convincing old-age make-up. That ancient version of the hero narrates the story, more or less, to a reporter (Daniel Mays) who is interviewing Nemo because he’s the last mortal human alive in a world where something called telemerization has created a population of quasi-immortals, each of whom has a personal lifeline to his or her own “stem-cell-compatible pig.”

But that’s really the only major science-fiction element to the film, which is closer to surrealist poetry — albeit inspired by quantum physics — than anything else. To be sure, there’s a whiff of time travel here. Not only does Nemo have the seeming ability to rewind time and correct past mistakes, but he also apparently splits, like an amoeba, into multiple versions of himself. Once he reaches adulthood, at least three different versions of Nemos exist simultaneously, with different houses, different kids and three different wives.

Anna, played by Diane Kruger, is the one true love of his life. Elise, portrayed by an astonishingly vulnerable Sarah Polley, is his painfully bipolar second choice. The union with Jean (Linh-Dam Pham), though loveless, has brought him the most material success.

The story — along with Nemo — hops around in chronology and location, with Nemo’s consciousness appearing to inhabit each version of himself at once. If it sounds confusing, it isn’t. It’s more exhilarating, in the manner of a carnival thrill ride.

Part of the thrill is the visuals. Van Dormael has crafted a saga that, even at two-plus hours, is endlessly, enormously watchable. Recurring images — a stray dead leaf, swimming pools, bathtubs and other bodies of water — create a rich visual rhythm and internal rhyme that make sure you’re never bored. Evocative period music is also used effectively as an emotional trigger, and not just to signal a time period. Almost every frame is a marvel.

As Nemo — or, rather, as the film’s many Nemos — Leto is quite fine. But along with Polley, the rest of the cast is also strong, with indelible performances by Regbo as Nemo’s adolescent self; Juno Temple as the teenage Anna; and Rhys Ifans and Natasha Little as Nemo’s parents, whose divorce precipitates Nemo’s schizoid psychological fissures.

Never mind that several characters seem to gain or lose British accents throughout the course of the film. The lack of continuity only enhances the sense of deliciously dizzying disequilibrium.

What is “Mr. Nobody” about? For one thing, it’s about that universal sense that life has passed you by, and the longing for the nonexistent reset button that will allow you a second chance. It’s also about the nature of time and causality, and the notion that many — perhaps infinite — different paths might coexist at the same time.

But more than that, it’s about the healing, and very human, power of the imagination. It is an old, old man who spins the twisted yarn of “Mr. Nobody.” “I don’t get it,” the reporter tells Nemo in frustration, after his narrative has, yet again, contradicted itself. “Did Elise die or didn’t she? You can’t have had children and not had them.”

In Van Dormael’s lyrical fantasia, it isn’t the truth that keeps Nemo alive, but his lies.

★ ★ ★ ★

R. At the AFI Silver Theatre. Contains obscenity, sexuality and drug use. 155 minutes.