In the world of Christopher Nolan’s latest mindbender “Inception,” thieves can steal secrets from the sleeping minds of their quarry by entering their dreams. A wealthy, mysterious industrialist named Saito (Ken Watanabe) approaches one such crew of mental mercenaries, led by the haunted and humorless Dom Cobb (Leonardo Dicaprio) and orders something a little off the menu: rather than stealing an idea, he wants the crew to implant one in the mind of a competitor. The initally reluctant Cobb only agrees to do the job after Saito offers to pull strings back in the United States and clear Cobb of pending criminal charges that prevent him from returning home to his children.

Cobb’s hesitance to take on this job is understandable. Not only is implanting memories more difficult to pull off because the subject must honestly believe the idea is his, but also it is far more dangerous – the thieves must delve so deeply into the mind of the subject that they risk being trapped permanently within the murky depths of their own subconscious… Don’t worry, you don’t have to fully grasp all this malarkey to enjoy the film.

And there is much to enjoy here. While the film is set in a world of idea theft, “Inception” itself is pleasantly chock-full of original, challenging concepts. Indeed, “Inception” breaks Hollywood’s most insidious commandment: big budget movies shalt not be about big ideas. If recent dunder-headed actioners like “The A-Team” and “The Expendables” are any indication, the studios seem to believe that big budget fare shalt not be about anything at all.

“Inception,” on the other hand, has a lot on its mind. Because one of Cobb’s past dream manipulations led to the death of someone he loves, he begins to seek solace by retreating deeper and deeper into his own dream world. As a result, the audience is left to wonder whether Cobb will ultimately choose the comforts of dreams over the lead-pipe reality of his real life.

Not only is the story’s substance challenging, but its form is boldly fractured, sections of its story float up into the narrative (as if from a dream), and Nolan trusts us to assemble the pieces correctly. To keep this film from becoming an action version of Robin Williams’ nauseously incandescent sudser “What Dreams May Come,” Nolan carefully grounds the dreamscapes in gloomy, almost black and white hues and sets the action in modern city environs. As a result, it is all the more jarring when these seemingly every day worlds reveal themselves to be fantasy.

So why three stars instead of four? Because the action in this thinking man’s action film is a bit of a dud. In part, this problem stems from the film’s premise. All the villains shooting at Cobb and his crew are anonymous, dream figments rather than flesh and blood baddies, and thus seem to exist only to be quickly dispatched by the good guys. However, the fault for these anemic action scenes also lies with Nolan, who seems so satisfied with the moving character work his narrative delivers, that he mailed in some really robotic chase scenes and a snow shoot-out so leaden I was reminded of Roger Moore-era Bond films. There is a nifty zero-gravity shoot-out in which one of Cobbs’ crew played by Joseph Gordon-Levitt has a tumbling brawl with a bad guy in a spinning hotel hallway, but that seems to be the only moment of action with an imagination as transcendent as the rest of the film.