Fans of wunderkind author Christopher Paolini’s mystical “Inheritance” series should race to see the film version of the opening chapter, “Eragon.” It’ll be Era-gone in a week.

A sword and sorcery tale told without the slightest whiff of screen magic, it is set in a land where men interact with special-effects dragons and little budget is left over for sets, lighting, costumes and crowd scenes.

The despotic King Galbatorix (John Malkovich at his hissiest) has exterminated his rivals, the freedom-fighting Dragon Riders, and seized the last egg of the near-extinct winged crocodiles. When it falls into the care of Eragon (Ed Speleers), hatching a little fire-breather, the farmboy finds himself thrust into the high-flying fight against tyranny.

Jeremy Irons plays Brom, a battle-wise rebel, Robert Carlyle plays Durza, the King’s warlock henchman, and Sienna Guillory plays Kiera Knightley, tomboying around on horseback and adding a halfhearted romantic angle.

“Eragon” is the first directing credit for Stefan Fangmeier, a longtime visual effects specialist with no discernable talent for supervising human performers. Whether staging intimate moment between actors’ or spectacular combat, they fall flat. Epic battle that should rock the theater look like high-sticking hockey scuffles, the cast converses in a welter of conflicting accents, and no one seems to be really connecting with any of their costars.

Ed Speleers commands a winged beast in the fantasy Eragon.

Irons delivers his lines in a campy croak, Carlyle hides behind a Marilyn Manson disguise of stringy wig and contact lenses, and Rachel Weisz, as the voice of the telepathic dragon, speaks in the bored, almost-quitting-time tones of a Starbucks barista. Speleers, in his screen debut, is attractive but insipid.

Whatever qualities made “Eragon” a tween best-seller are missing from this adaptation. The film lacks the simplest kinds of competence. There is no sense of chronology. Does it all take place over the span of a week? A summer? A year? How is it that magicians can cause dozens of axes to fly off a wall toward a foe, but can’t make them hit the target?

As the film’s grip on your attention weakens, you find your thoughts drifting to the mysterious source of the radiant backlighting in the nighttime forest scenes, and the remarkably generic action-adventure score that fails to ignite the fight scenes.

After “Eragon,” even die-hard dragon fans will be draggin’.