Christopher Nolan supposedly started writing Inception a decade ago, when he was making Memento. I can see how it would take a long time to write. The labyrinthine dream-within-a-dream-within-a-dream structure of Inception would have made rewrites confoundingly difficult. And in between, Nolan was writing and directing other complex films like The Prestige and The Dark Knight. Nolan has a real knack for reinventing fundamental genre films, whether it’s superhero movies or detective stories or, in the case of Inception, espionage films.

The plot of Inception is simplicity itself; the execution is mind-bogglingly complex. A corporate spy/con artist named Cobb (Leonardo DiCaprio) steals secrets from people. He’s also in trouble with the law, and separated from his young children, whom he desperately wants to see again. The reason for Cobb’s troubles has to do with his methods for extracting information from his marks: He infiltrates their minds and steals the ideas he finds therein.

This involves a complicated process requiring sedatives, some kind of mind-linking machine and a dream architect who builds the subconscious landscapes in which Cobb and his team do their spy work. These dreamscapes tend to be pretty pedestrian, and so are the actions in the dreams. Foot chases, unexpected plot twists and familiar faces all turn up. And this is also true: In a dream, you don’t know that you’re dreaming (that was Descartes’ argument, anyway), so Cobb’s victims never realize that they’ve been robbed.

Cobb knows when he’s dreaming and when he isn’t – although it may be the case that he’s losing his mooring in reality, tripping on the dream/reality line. Some Cartesian skeptical confusion plays a key role in complicating Cobb’s life, and is embodied (in his dreams) by his wife Mal (Marion Cotillard), who, for reasons that I won’t divulge, tends to turn up at the most inopportune times while he’s at work.

Cobb’s latest assignment is one that almost everyone thinks is impossible: inception, or implanting an idea in another person’s mind. A powerful Japanese businessman named Saito (Ken Watanabe) hires Cobb to implant an idea in the mind of Robert Fischer (Cillian Murphy), the heir to a vast business empire. Saito wants Fischer to break up his corporation; Cobb’s role is to plant the germ of an idea that will grow so organically that Fischer will think that he thought of it himself. Inception is far more complicated and dangerous than just swiping information, and Cobb knows the dangers first-hand: It’s an unpredictable process because once an idea takes hold, it takes on a life of its own. He takes the job because Saito promises to fix his problem so that he can be with his kids once more.

And so, in true con-movie style, Cobb assembles a team: There’s Arthur (Joseph Gordon-Levitt), his right-hand man; Eames (Tom Hardy), a forger who’s good at being someone else; Yusuf (Dileep Rao), a creative pharmacist; and Ariadne (Ellen Page), a young architect who is good at creating spaces. Cobb auditions the new recruit Ariadne (named after the Ariadne who helped Theseus escape the Minotaur’s labyrinth?) by asking her to design a maze.

Nolan designs a complicated multi-level labyrinth with Inception, with interlinked layers all operating in their own separate dream-space and dreamtime. What happens in one subconscious layer affects what happens in the layers above and below it: The dreams within the dreams unfold independently, but with their gears linked so that when one turns, so does another. But reality (such as it is) slips in, too; it’s a running gag in the movie that one character’s full bladder means a torrential downpour for the duration of the dream. Something that can infiltrate every layer simultaneously – providing a kind of constant and signal for the dreamers – is music (Edith Piaf music, to be precise, bringing to mind Cotillard’s best-known role).

Cinematographer Wally Pfister, who has been behind the camera for all of Nolan’s features since Memento, does exceptional work in Inception, in a vast array of spaces: bright beaches and crumbling cities, hotel rooms, elevator shafts, warehouses, the inside of a van during that torrential downpour. What Inception doesn’t do is trade in fanciful, surreal, irrational dreamscapes of the sort that only exist in movies – those, Cobb tells Ariadne, can tip off the dreamer-target, triggering the mind’s rational defenses (the moviegoer’s, too).

Part of what makes Inception work so well is that the dreams are mostly so ordinary, as most dreams are. They are anchored in reality, but also infiltrated by movies. This makes sense, given how dreamlike movies have always been, but also how movielike dreams (or at least my dreams) can be. The stuff that happens to Cobb and company is the stuff that happens in, say, James Bond movies – shoot-‘em-ups in the Alps, crazy-cool car chases – but also Matrixy stuff like zero-gravity fight scenes (how do you pound a guy when there’s no gravity?). The story manages to integrate, in a logical way, some pretty cool special effects, too – like a city that folds over on itself, and an Escherian infinite staircase.

Inception is an entertaining puzzle; the dream-within-a-dream (movie-within-a-movie) multilayer structure is demanding. Teasing apart the layers, keeping the whole tangled web straight, requires more attention than your run-of-the-mill industrial espionage caper. Inception is smart and original – a nonderivative, non-remake, non-sequel, brand-new thing that’s constructed out of familiar pieces assembled in an uncommonly imaginative way.