By now, you’re either invested in the Twilight movies or you’re not.

If you’re a reader of Stephenie Meyer’s novels, eager to see her ever-expanding world of ageless vampires, hotheaded werewolves and hormonal teenagers evolve on the big screen, or merely seduced by Robert Pattinson’s smoldering glower and Taylor Lautner’s sculpted physique, you’ve probably been anticipating Eclipse since November’s New Moon.

The good news: Eclipse, for all its laughably clunky dialogue and overwrought melodrama, is easily the most engaging Twilight adaptation to date, a deftly paced thriller that feels appreciably leaner than its predecessors.

Here, director David Slade (30 Days of Night) and returning screenwriter Melissa Rosenberg have trimmed much of the fat from Meyer’s self-indulgent prose and produced an undercooked but enjoyable romance. It’s as weightless as popcorn, and its fleeting pleasures are no less savory.

At last, it answers the question, posed by New Moon, of which suitor Bella (Kristen Stewart) will choose: Edward Cullen (Pattinson), the eternally gloomy vampire with a heart of gold, or Jacob Black (Lautner), his fiercely passionate, perpetually shirtless rival, who happens to moonlight as a wolf.

It took three movies, but Bella’s dilemma finally resonates on a human level. Picking between two studs is hard enough, but hers is a more thought-provoking conundrum. Should she sacrifice her humanity and youth to join Edward’s family among the undead?

Bella seems to think so, but Edward isn’t so sure. Neither is Rosalie (Nikki Reed), Edward’s adopted sister, whose violent initiation into the Cullen clan, effectively recreated here, dashed her lifelong dream of motherhood. It’s a jarring sequence, and it lends Rosalie and her family a depth lacking in previous installments.

If the movie’s bizarre love triangle leaves you cold – understandable, considering that Bella, for all her natural beauty, reacts to life as one might a never-ending root canal – the action is surprisingly intense. Slade knows how to stage a fight, and the climactic showdown between Bella’s sworn protectors and a pack of rogue vamps led by the nefarious Victoria (Bryce Dallas Howard) is delightfully vicious.

None of this makes Eclipse anything more than an agreeably far-fetched teen fantasy, something Slade slyly acknowledges. By punctuating Bella’s hand-wringing histrionics with moments of comic relief, often provided by her world-weary dad, played by a winking Billy Burke, and Lautner, whose six-pack is as much a selling point as a running gag, Slade strikes a pleasing balance that future Twilight directors might well find instructive.