Seth Grahame-Smith’s “Pride and Prejudice and Zombies,” published in 2009, was a title that didn’t really need a novel. Essentially a reprint of the Jane Austen classic with sudden passages of slaughter, it was a good gag that instantly wore thin, the literary equivalent of a Billy Big Mouth Bass.

Here comes the inevitable film version, written and directed by Burr Steers. It arrives long after the peak of AMC’s “The Walking Dead” and in the wake of countless zombie movies like the comedy “Scout’s Guide to the Apocalypse” and the rom-com “Warm Bodies.” It also arrives in February, usually a graveyard for dead-on-arrival releases.

advertisement | advertise on newsday

All of which makes “Pride and Prejudice and Zombies” an unexpected treat. What could have been a one-joke film turns out to be an entertainingly weird mix of BBC-quality costume drama and lowbrow horror flick. What’s most surprising are the excellent actors — some drawn from the British stage — who play even the most ridiculous scenes absolutely straight. Against all odds, “Pride and Prejudice and Zombies” avoids becoming an Austen travesty and almost qualifies as a credible adaptation.

All the familiar figures are here, beginning with the strong-willed Elizabeth Bennet (Lily James, of “Cinderella”) and her sisters. Like most ladies of this zombie-plagued Regency, they are trained in martial arts as well as polite conversation, and the film has some kinky fun peeking into their bedchambers while they strap daggers to their thighs. Sam Riley (“Control”) is perfectly cast as brooding zombie hunter Colonel Darcy, while Matt Smith (of “Doctor Who” fame) steals the show as a comedic, possibly closeted version of Parson Collins.

Steers uses two simple tricks to juice up Austen’s novel of manners. One is to transform dialogue into action whenever possible. A verbal spat between Elizabeth and Darcy, for instance, becomes a physical altercation with swords, knives and chokeholds. (It’s easily the film’s funniest and cleverest scene.) Steers also repeatedly directs his heroines to save their beaus’ necks in battle. That feels a bit calculated, but as the logical extreme of Austen’s feminism, it works.

The movie eventually flags, though only in its final third. That’s a feat in and of itself. For an undead version of Austen, “Pride and Prejudice and Zombies” has far more life than you’d expect.