“Inception” is a work of staggering imagination that’s almost undone by its very coolness.

What it accomplishes is phenomenal. And yet on a fundamental dramatic level it feels vacant, an awesome display of filmmaking brio that offers plenty for the eyes, ears and head but precious little for the heart.

The latest from Christopher Nolan (“Memento,” “The Dark Knight,” “The Prestige”) practically defies description. It’s a metaphysical crime caper/action epic that unfolds almost exclusively in the dreams of its characters.

Dreams, of course, are where anything can happen, where the subconscious comes out to play or to torment itself, where our deepest fears are manifested.

In the near future of “Inception” our dreams can be invaded. Cobb (Leonardo DiCaprio) is a corporate spy skilled at “extraction.” Using a briefcase-size machine (it’s like a fancy lie detector with wires to connect the participants), he and his colleagues can enter the dreams of a sleeping target and root around for the deepest secrets.

This is no simple task. Cobb and his team create dream environments and scenarios so real that their drugged subjects don’t suspect they’re asleep, yet so subtly calibrated that they push just the right emotional and intellectual buttons. When subjects wake up, they have no memory of being violated; Cobb walks away with valuable information.

But Cobb is an international fugitive, accused of murder and unable to re-enter the United States to be with his two young children. This makes him vulnerable to the entreaties of the powerful industrialist Saito (Ken Watanabe), who recruits him to go after Fischer (Cillian Muphy), the heir to a rival conglomerate.

Instead of just extracting information, though, Saito envisions a far more dangerous “inception” — planting ideas into Fischer’s subconscious, ideas that would lead him to sell off his family’s extensive holdings.

If Cobb can accomplish this, Saito will pull strings to ensure his safe return home.

Nolan’s screenplay has two main sections. In the first, Cobb and his associate (Joseph Gordon-Levitt) recruit a new team — Ellen Page, Tom Hardy, Dileep Rao and Watanabe — and begin building the dream world in which they will operate.

The second half of the film is the actual job, and it’s truly mind-blowing, a labyrinth of dreams within dreams within dreams. The stakes are high. In a standard extraction, when a dream spy “dies,” he simply wakes up in the real world. But should you die in the ever-deeper levels of an “inception,” you’ll find yourself in limbo, unable to return to our dimension.

Things are further complicated by Cobb’s own iffy mental state. Though he has kept it a secret from his colleagues, while on the job he’s often visited by his late wife and former extraction partner (Marion Cotillard), who may appear as a lover or as a gun-toting adversary. She’s obviously a manifestation of Cobb’s own tortured conscience, and her presence threatens everything.

Yeah, that’s a lot to wrap your head around. But Nolan is such a skilled storyteller that it all somehow makes sense. He finds ways to delineate between the ever-descending dream environments Cobb’s team must navigate so that we can sense just where we are at any moment.

And these dreamscapes make for some dazzling moments, like a brawl between Gordon-Levitt’s character and several thugs in a gravity-free hotel hallway. It’s like “The Matrix” on steroids; you can hardly believe what you’re seeing.

Somewhat more prosaic, and wearisome, s a dream level that consists of a fortress on a snowy mountainside, guarded by an army of troops on skis. It’s a bit too much like a James Bond movie.

Nolan’s filmmaking sleight of hand is so slick that for much of “Inception’s” 2 1/2-hour running time we’re breathlessly diverted. But eventually a sort of numbness sets in. Beneath the astonishing visuals and mind-bending ideas there’s no real emotional hook.

With the exception of Cobb — and nobody sells angst like DiCaprio, remember “Shutter Island”? — the characters are all ciphers. We know virtually nothing about these one-noters, so we aren’t invested in their fates. They might as well be pawns in a game of chess.

Like his extractors, Nolan relishes messing with our minds. It’s entirely possible that there is no “reality” in “Inception,” that the film’s “real world” is just another dream state experienced by Cobb. Expect a flurry of scholarly papers, not to mention countless colorful smoke-filled late-night bull sessions.

Nolan is a very clever fellow, no argument there. He’s skilled at juggling big ideas and making us think. Now if he can just make us feel.

Film focus

WHAT: “Inception”

RATED: PG-13 for sequences of violence and action throughout

RATING: 2 1/2 stars

RUNNING TIME: 2 hours, 28 minutes

Leonardo DiCaprio and Ellen Page appear in a scene from “Inception.”