For someone not versed in Stephen King’s self-described “magnum opus,” the movie adaptation of King’s “The Dark Tower” is a hopeless mess, a truncated tale of heroes and villains tied into a tangled knot of inexplicable mythology.

Those who have read King’s books, I suspect, will split into two camps: those who recognize the many references director Nikolaj Arcel tosses into this weird mix of urban action and fantasy monsters, and those who will rage over what a hash has been made of King’s work.

On a gray planet, children are funneled into a sinister oily pyramid, strapped to chairs that suck out their life force. That energy forms a beam that hurtles into the sky and toward a massive black tower. Every time the beam hits the tower, the shockwaves are felt everywhere — even on Earth.

The quakes have a particular effect on a Manhattan 12-year-old, Jake Chambers (Tom Taylor), who links the tremors to the disturbing images he sketches of the pyramid, an evil Man in Black and a heroic Gunslinger. Jake’s mom (Katheryn Winnick) and his shrink (José Zuniga) blame the visions on lingering grief over his firefighter father’s death and try to get him committed to a clinic upstate.

When the people from the clinic arrive, though, Jake sees they’re part of the evil world of his nightmares. He escapes and seeks out a rundown Brooklyn building he saw in his nightmares. The building, he finds, houses a portal to the first planet, where Jake finds Roland Deschain (Idris Elba), the last of the Gunslingers.

Roland informs Jake of the Gunslingers’ mission to protect the Dark Tower, which shields many worlds (including ours) from the forces of darkness — embodied by the Man in Black, aka Walter (Matthew McConaughey). Roland is driven to kill Walter, who killed Roland’s Gunslinger father (Dennis Haysbert). And Walter is determined to capture Jake, whose mental energy is powerful enough to be harnessed in that pyramid and topple the Dark Tower at last.

That’s a lot for one movie to digest, but still Arcel (“A Royal Affair”) and co-writer Anders Thomas Jensen, both big names in Denmark, make it feel choppy and abbreviated — neither a summation of King’s seven-novel series nor a continuation of it. (Arcel and Jensen share writing credit with Hollywood veterans Akiva Goldsman and Jeff Pinkner, suggesting this series has been bouncing around Hollywood for a long time.)

While setting up the many worlds of King’s saga, Arcel also sets the movie firmly in King World. Fans of the writer will find plenty of Easter eggs, with references to King titles such as “The Shining,” “It,” “The Shawshank Redemption” and “Christine.” But those mostly serve as a distraction from the jumbled story at the center of the movie.

The stars bring the heat, though. McConaughey is all suave menace, even if he looks as if he’s shooting Lincoln Town Car commercials between takes. Elba has a heavier burden, having to embody King’s mythic hero and also name-drop the author’s mythic references (such as King Arthur’s Excalibur), but he mostly shoulders it with grace and some charm.

But none of these stars’ “magicks” (a word the Man in Black uses way too often) is enough to save “The Dark Tower” from its labyrinthine plot machinations and annoying storytelling shorthand. It’s that rare movie that simultaneously feels too short and too long, but never just right.

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’The Dark Tower’

Stephen King’s “magnum opus” is translated into a jumble of fantasy ideas lumped into a confused mythology.

Where • Theaters everywhere.

When • Opens Friday, Aug. 4.

Rating • PG-13 for thematic material including sequences of gun violence and action.

Running time • 95 minutes.