The first half of this is dynamite. Though the concept is derivative of any number of sci-fi conceits, Bong’s visual imagination lends the hoary old scenario some striking imagery — a masked army wielding hatchets, a man with a flash-frozen arm, Tilda Swinton whipping out a denture — and while he’s not the world’s greatest action director, he does know his way around a bloody set piece.

The central metaphor — a passenger train running around the world in infinite circles gives the swells the run of the front cars and relegates the poors to the back — just keeps chugging along for most of the film’s running time but eventually starts to creak under its weight and call attention to its artificiality. (As someone on my Twitter feed asked: do the kids have to walk through the rave every day on their way to school?* However, when the schoolteacher turns out to be an absolutely ferocious Alison Pill, I can forgive all kinds of artifice.)

It really does run out of steam once it reaches The Hall of the Exposition King and lurches toward not a happy ending but at least a hopeful one. Still bracing. Terry Gilliam would have had a field day with this material — and Bong knows it, which is part of what makes the whole production so much fun. I want to call it the best science-fiction movie of the year (take that, Dawn of the Planet of the Apes) and then I remember Under the Skin and I nod solemnly and shiver a little. That’s a science-fiction movie. (Technically a 2013 release? Note to self.) But this one is really good, too. And the one about the apes isn’t even half-bad. Imagine, a cycle of excellent SF films in 2014. What did we do to deserve this?

* Judging from this diagram, I guess the answer is “No,” but it sort of feels like that’s the case when you’re watching.