Nolan's latest outing, his first solo screenwriting credit since his debut feature Following, is heavy duty science fiction, densely plotted and filled with fresh, exciting ideas.

That's the good part. I'll get to the not-so-good part in a minute.

Inception follows a team of "extractors" – criminals who use technology to infiltrate the literal dreams of corporate executives, then steal their ideas for rival companies – who have been assigned an unusual case: to go inside the head of a young executive (Cillian Murphy) in order to plant an idea there. It's a tricky maneuver known as, you guessed it, an "inception".

Leonardo DiCaprio, leading an all-star cast, agrees to the job if it means he will be allowed back in the United States to be with his children. (Why he had to leave the US is something I won't reveal here.) What unfolds is a mind-bending heist movie with shades of James Bond, The Matrix, even Solaris, as Leo's own demons follow him into other people's dreams, and put him and his team at risk of a fate possibly worse than death.

Nolan's script is dizzyingly complex, though the story flows fairly logically without losing the audience. It was only after the film was over that I started counting all the problems I had with it. To name most of them here would be to spoil much of the plot, but a general issue I had is that the "dream world", as Nolan depicts it, has little relation to the actual dreams we all experience.

Nolan's defense may be that his team of idea thieves are not entering a person's dream already in progress, but manufacturing said dream out of whole cloth. So if your high school English teacher doesn't make an appearance, or if you aren't suddenly naked, it's because you're not in control – Leo and company are.

Still, there seems something missing in this all-too-literal dreamscape of Nolan's. A sense of fantasy, perhaps. Or surprise. Or even surrealism: early on, Ellen Page's character, drafted as an "architect" with the job of creating the dreamer's world, does some nifty landscape modeling, but the visual coolness of this idea is almost instantly negated when DiCaprio warns her not to invent anything too weird-looking, or else the dreamer's "projections" – the movie extras who populate the dream's background – will get suspicious and even attack. Uh, and why is that? It's one of many plot contrivances that don't make sense in the long run: after all, if these "extractors" can build the world, then why can't they control the "projections"?

Similarly, there's a moment where Tom Hardy's character – a "forger", or shape-shifter – pulls out a comically huge gun, telling Joseph Gordon-Levitt, "You have to dream bigger, darling." It's a cute moment that sheds light on the potential for the dream team to do whatever they want – after all, if a whole city full of projections is already attacking you, there's no reason you can't start flying or become 100 feet tall, since you're no longer trying to evade attention – but again, Nolan drops this idea as quickly as he introduces it.

There are many other details which Nolan intentionally does not address: is this "dream-sharing" technology so commonplace that everybody knows about it? Is that what Michael Caine, playing DiCaprio's father, is teaching in Paris? Why is Page so adept at constructing dreams within dreams within dreams, even though she's a neophyte?

The main problem with Inception is that Nolan's head is bursting with so many ideas that, in his scramble to squeeze them all into a breathlessly paced storyline, a few are over-explained, some contradict themselves, and many are inadequately explored. To further confuse things, Nolan attempts to balance the sci fi thrills with genuine human emotion, although only DiCaprio and to a lesser extent Murphy are given any depth to their characters.

Still, during the two and a half hours that I was watching Inception, I was quite impressed with the concept, the cast, Nolan's filmmaking craft, and of course the awesome visuals, though I wish the story wasn't so dad-gummed serious about everything. Both Nolan and DiCaprio try too hard for profundity in their work. I hope they each find some room to lighten up. It is possible to tell a dramatic – even gripping – story without wallowing in gloom.