Leonardo DiCaprio stars as an expert in the world of corporate espionage who steals secrets from the minds of those who are dreaming in Inception.

A good fantasy film creates a wholly original world or concept convincingly. A good science-fiction film asks questions about our humanity while bending the laws of nature. “Inception” is all of this and more.

In fact, “Inception” is essentially a heist movie. While it never really explores the immorality of planting suggestions in the brain of its one specific victim, it does have a field day pointing out the dangers of this process — called inception — by gazing deep into the tortured soul of corporate dream extractor Dom Cobb (Leonardo DiCaprio).

In a weird coincidence, it’s the second DiCaprio movie this year (following Martin Scorsese’s underrated “Shutter Island”) that hinges upon a disturbing unreality, a last-minute twist and his character’s sense of guilt surrounding a wife and kids.

“Inception” is also an action film. But this kind of thematic depth isn’t common in this genre and especially not this time of year. Writer/director Christopher Nolan (“The Dark Knight,” “Memento”) orchestrates the entire ambitious movie like it’s the all-or-nothing back page of the coach’s playbook. It’s complicated and risky and everything has to go just as planned, but if it works, the payoff is everything.

First, Nolan sets up the rules. And after a crackerjack opening scene that sucks you right in, this is the only part of the movie that feels a little lifeless. “Inception” is bogged down by at least a half-hour of lengthy exposition. Nolan is the stodgy guy at the party who insists on reading the directions while everyone’s impatient and eager to start the game.

Without understanding the basic concept, however, it’s impossible to grasp the dramatic complexities of the script, which keep piling on. Dom and his partner (Joseph Gordon-Levitt) are used to searching for secrets buried within the subconscious, but their newest challenge is to go into someone’s mind and plant an idea that will remain once the person (Cillian Murphy, the inheritor of his father’s multi-million dollar fortune) has awakened.

Ellen Page, who plays a newbie dream “architect,” functions as our stand-in, asking questions just when we need answers. And believe me, we do need them. Almost immediately as the rules have been established, Nolan delves deeper and deeper into the world he’s created as his characters literally do the same in various dream states. The way this plays out is pure cinema.

“Inception” dazzles with a visual inventiveness that subtly blends CGI with in-camera effects to make everything more relatable, no matter how far out things have gotten. Nolan saves the big guns for last, conducting an ambitious final act that’s spread out between multiple perceptions of time and dream states.

What’s truly amazing is this: Despite the fact that some details of the labyrinthine plot are simply too obscure to comprehend on a first viewing, Nolan sells the emotion — and the consequences — visually. It’s just like our dreams. Even if we don’t fully grasp every detail of what has transpired, we instinctively understand the basics of what has transpired.

Have you ever woken up from a dream feeling a terrible sadness and not been able to pinpoint why? There are scenes that play out that way, particularly those involving Dom’s wife (a menacing Marion Cotillard). Characters don’t act like real people because they are figments of the dreamer’s imagination. They don’t need to make sense. They inherently don’t make sense to anyone else — and that’s when things get dangerous.

Without centering the movie on Dom’s own personal journey and his own sketchy motives (a shrewd storytelling move to make our hero as dodgy as he is), the audience wouldn’t have someone to root for within this mind-bending maze. And despite the fact that he puts his entire team into danger, we long for Dom’s personal story to be resolved.

In other words, this ain’t Freddy Krueger.

The problem with creating drama out of a world of dreams is that anything can happen. If there are no limits, there’s no real danger. Nolan sets limits and adheres to them. Like “Memento,” “Inception” is a big puzzle that your mind works overtime to figure out while the movie also entertains on less intellectual levels. (Cue a snowbound action scene with bad guys on engine-powered sleds!)

Underneath it all, “Inception” is another in a long line of films where the main character has to do “one last job.” If movies tend to revolve around the defining moments in peoples’ lives, though, then why not trot out this sturdy genre tenet? After all, it’s not like that idea is the only thing the movie has going for it. “Inception” practically begs for multiple viewings just to see if it can all hold up from a narrative standpoint.

The lengthy, tense final act may go down in film history as one of the most complicated balancing acts ever put on film. The fact that Nolan is able to keep an audience enthralled during the entire thing with very little dialogue is a testament to his prowess as a visual storyteller.