At first blush the idea of a zombie version of “Romeo and Juliet” might sound like a terrible idea—okay, does sound like a terrible idea. But Jonathan Levine pulls it off with considerable agility and even sweetness in “Warm Bodies,” aided in no small measure by a winning cast.

Adapting Isaac Marion’s young adult novel, Levine (“The Wackness,” “50/50”) finds precisely the right way to treat the premise, avoiding a point-by-point, slavish translation of Shakespeare into genre-movie terms but retaining enough of the source (the heroine’s name—Julie—though the zombie hero can remember only that his starts with an R, along with a balcony scene) to make its indebtedness cheerily obvious. And the tone he adopts, despite some serious undercurrents (like the character of Julie’s father General Grigio, who’s constructed a non-zombie oasis in the middle of the city and is determined to defend it at all costs), is overall surprisingly light and whimsical. That’s a blissful contrast to the deadly earnestness of the inter-species romance of “Twilight” and its ilk.

Of course, Levine couldn’t sustain the picture’s conceit for long were it not for a cast who can carry it. Nicholas Hoult, a child actor who won plaudits for his work in “About a Boy” (2002) and more recently showed he was making the transition to adult roles well with an excellent supporting turn in “A Single Man,” is extraordinary as R. He’s helped by the amusingly deadpan narration Levine has provided for the character, which Hoult delivers in wry voice-over. But he’s also a nimble physical presence, nailing the zombie gait but, more importantly, sensitively capturing the subtle changes the fellow experiences after meeting Julie (spunky Teresa Palmer).

That happens when the girl leaves her father’s walled compound along with a small band, including her boyfriend Perry (Dave Franco), to collect needed medical supplies from the devastated areas occupied by those they call the “Corpses”—both zombie-like types like grunting R and his best buddy M (Rob Corddry), who will eat the brains of the living to enjoy experiencing their memories, and even more downgraded specimens, the skeletal Bonies, who will devour anything with the slightest glimmer of life remaining. When the explorers fall prey to the Corpses, R saves Julie from being eaten after he’s consumed Perry’s brain and takes her to the relative safety of his idiosyncratic abode in a junked airplane that he’s filled with items he’s collected and hoards—like old LPs that he plays for his houseguest (with the songs providing amusing counterpoint to the action).

That includes R’s increasing recovery of his humanity in light of the feeling he has for Julie—which includes a growing ability to speak again, though haltingly—and her gradual warming to him. Soon they’re off on a journey back to her father’s compound, and though they’re separated on the way, he follows her there despite the danger after he learns—from Corddry and the other Corpses who are undergoing transformation to more human status, too—that the Bonies are planning a massed assault. Despite the misgivings of Julie’s father—whose actions allow for something akin to Shakespeare’s tragic finale, though with the happy twist Levine’s take on the story demands—the humans and the increasingly humanized Corpses find they have a good deal in common.

Visually the film creates a convincingly dystopian world for this tale to take place in. The production design by Martin Whist is aces, especially in view of what must have been a comparatively modest budget, with many witty details on the edges of the frame, and it’s complemented by Javier Aguirresarobe’s widescreen cinematography, which uses a bleached-out look to the images while allowing nice touches of color, like R’s tattered red hoodie.

In the movement to put new spins on old horror-movie conventions, makers of zombie pictures have been among the most inventive. With “Zombieland” Ruben Fleischer turned the genre toward screwball action comedy, and now Levine pushes it in a surprisingly charming and funny direction. “Warm Bodies,” like Hoult’s R, occasionally stumbles along the way, but for the most part it’s a jaunty, even touching journey.