A big-bang demolition derby, J.J. Abrams’ much-anticipated, greatly enjoyable Super 8 seems bound for box-office glory. Set in a small Rust Belt town during the summer of ’79, Super 8 basically refracts— or re-refracts—a familiar ’50s sci-fi trope, even as Abrams riffs on the freshly minted sense of suburban wonderment that Super 8 producer Steven Spielberg brought to the material in the late ’70s and early ’80s. Newly motherless Joe Lamb (neophyte Joel Courtney) is making a Super 8 Night of the Living Dead with a bunch of fellow 14-year-olds. The kids are out late one night, secretly filming by the town railroad, when a pickup truck apparently stalls on the tracks, precipitating a massive, flaming-boxcar-hurling, apocalyptic derailment of terror. Before long, unseen whatzits are liquidating various characters, stealing car engines, cutting the electrical power, and frightening the town’s dog population into scampering for neighboring counties. The U.S. Army, even more sinister here than in Close Encounters or E.T., takes control, leaving legitimate, if overly uptight, authority to Joe’s father (Kyle Chandler), a local deputy sheriff. “This feels like a Russian invasion,” someone insists at a chaotic town meeting—and that’s before the army’s red-faced commander (Noah Emmerich) orders a mass evacuation. Soldiers are ubiquitous but, as in Cloverfield, Abrams rations the whatzit appearances in fragmentary bits and pieces. The movie manages to keep its secret for nearly 90 minutes, and, although not hard to figure, you won’t read it spelled out by me.