“The 5th Wave” is very much a January release — in another words, not very good — but at least it’s unusual in its awfulness. For its first half hour, the movie is interesting and alarming in the best way, laying down a sci-fi premise and delivering on it with convincing detail. Rarely does a movie that fails so utterly start so well. The filmmakers understand something about the end of the world: If it were to start happening, people would resist admitting it until the last possible moment and probably even beyond that. The human capacity to adapt while denying the obvious isn’t infinite, but it’s close, and so the movie’s early scenes, in which aliens launch waves of attack, while people strive to adjust and maintain their normal schedules, have an unsettling whiff of truth. To watch it is to feel that yes, if this ever happened, it would probably go just like this.

Anyway, for three waves, “The 5th Wave” is a terrific picture, but those opening waves come fairly quickly. The first one is the jaw dropper: After parking in the sky for just long enough for people to think, “Maybe these visitors just want a parking space,” the aliens set off an electromagnetic wave that cuts off every engine, every machine and every device, so that cell phones go dark and planes fall out of the sky. All this is seen through the eyes of a high school girl, Cassie (Chloe Grace Moretz), who watches with a mix of terror and stupefaction. To a lesser extent, so does the audience.

Wave two and three aren’t bad, either. Wave four pretty much happens off screen, and then somewhere between waves four and five, the movie slowly — and thoroughly and irrevocably — falls apart. The collapse comes as the result of an epic miscalculation: With the human race facing annihilation, how much should you care about a high school girl’s blossoming romantic interests? Not at all? Or slightly less than that?

For an entire half hour “The 5th Wave” is able to disguise what it’s selling, but once you catch on, you catch on: This is the teen apocalypse. This is Armageddon goes to the prom, not literally, but in spirit. If only it were literally about Armageddon and the prom — if only it were crazily obvious — “The 5th Wave” might have had the virtue of silliness.

Instead it has the curse of earnestness. It is so sincere … It is so sincere it could put you into a coma. Have you ever dreamed with your eyes open? Have you ever sat in a theater wondering who keeps snoring, only to wonder if it might be you? There are new experiences to be had here, not experiences that you’d want, but experiences.

Oh, and by the way, the movie doesn’t end. It simply stops. You see, “The 5th Wave” is the first book in a trilogy by Rick Yancey, and if we’re not really vigilant, and look to the skies, and prepare, they’re going to make at least two more of these things. We’ve got to beat back the invasion now, or the aliens are coming back.