Another weekend, another movie adapted from a young-adult novel about a dystopian future in which a spunky teen heroine learns to fight her oppressors. Less ambitious and pricey than “The Hunger Games” or the “Divergent” flicks, this initial installment of Rick Yancey’s ongoing trilogy about an alien attack on earth plays like a Disney Channel version of “Invasion of the Body Snatchers” or “The Invaders,” the sixties Quinn Martin ABC potboiler inspired by it.

After a prologue introducing Cassie Sullivan (Chloe Grace Moretz) as a typical Ohio high schooler infatuated with campus football star Ben Parish (Nick Robinson)—who, of course, barely notices her—the world abruptly changes with the arrival of a huge spacecraft circling the globe but conveniently stopping right above the Sullivan home. Cassie’s darling little brother Sam (Zackary Arthur) is fascinated, but her dad Oliver (Ron Livingston) is considerably less sanguine about what it portends, and it turns out he’s right.

The unseen aliens, who are soon dubbed (rather unimaginatively, “The Others”), launch a series of calamities, or waves, designed to eliminate humanity. The first eliminates all terrestrial power, sending cars crashing into each other and planes falling from the sky and ending electrical service and telecommunications entirely. The second unleashes earthquakes and tidal waves in some pretty weak CGI. The third is a virus that carries off large numbers of people, including Cassie’s mother Lisa (Maggie Siff), though the other Sullivans remain immune to its effects. They decide to decamp for a survivors’ camp, which provides a rustic oasis until troops from a nearby Air Force base led by Colonel Vosch (Liev Schreiber) show up. They take all the children, save for Cassie (who’s late to the bus because she’s retrieving Sam’s teddy bear), to the base; and she witnesses a melee in which the adults, including Oliver, are mowed down by the soldiers—the result of Vosch’s revelation that the fourth wave involves the aliens taking over human hosts and using the bodies to kill survivors, and the camp residents attempting to escape before they can be tested for alien control.

The rest of the film follows Cassie’s efforts to make it to the army base and reunite with Sam, who’s been drafted into a squad of young fighters by kick-ass Sergeant Reznik (Maria Bello)—a squad that just happens to be led by Ben, now nicknamed Zombie, and includes a hardboiled Goth girl called Ringer (Maika Monroe). While they train to fight the camouflaged Others with automatic weapons and visors that can reveal the aliens controlling their human hosts ensconced in their brains (more poor CGI), Cassie—who’s attacked by a sniper—is befriended and nursed back to health by handsome hunk Evan Walker (Alex Roe), who insists on accompanying her on her quest.

The narrative brings a number of twists as the two plot threads proceed, but sadly none of them prove especially surprising, and they’re resolved with ridiculous ease anyway, in a big finale that brings characters together in extremely implausible ways and allows them to achieve a victory that exhibits more spunk than cleverness. The most notable—and frankly disquieting—aspect of the script is the notion of youngsters being used as front-line fighters in the war against “the enemy.” With the tragedy of child soldiers in Africa all too real (and recently dramatized to harrowing effect in “Beasts of No Nation”), the casual employment of this plot point, even if it is eventually turned to the advantage of humanity, feels tasteless. Of course, that’s the whole point of “The 5th Wave”—it’s basically “Red Dawn” with aliens instead of communists. But that doesn’t make the premise any less disagreeable.

That said, the movie is decently if unspectacularly made. J Blakeson’s direction is adequate, an adjective that applies equally well to Jon Billington’s production design and Enrique Chediak’s cinematography; and if Moretz is no Jennifer Lawrence (and Cassie no Katniss), the “Kick-Ass” star has a degree of personality many actresses of her age lack. Neither Robinson nor Roe brings a great deal to the party beyond good looks and doe-eyed glances, and Monroe’s tough-girl posing gets tiresome quickly, but Schreiber and Bello bring a note of authority to the juvenile proceedings. Arthur is cute as a button at lovable Sam, and Talitha Bateman isn’t far behind as another petite squad member nicknamed—if you can believe it—Teacup.

Quality-wise, “The 5th Wave” is reminiscent less of “The Hunger Games” than of Andrew Niccol’s pallid screen version of “Twilight” maven Stephenie Meyer’s “The Host.” Whether the series will limp on to the two further installments is doubtful.