Like “The Notebook,” but with an elephant, the unexpectedly good film version of “Water for Elephants” elevates pure corn to a completely satisfying realm of romantic melodrama.

This adaptation of the Sara Gruen best-seller, set in a storybook edition of Depression-era 1931, stars Robert Pattinson of the “Twilight” franchise as Jacob, the earnest son of Polish immigrants, “a veterinary student from the wrong side of the tracks” as 20th Century Fox’s publicity describes him. A tragic off-screen accident renders him an orphan not long into the picture. Broke and distraught, the Cornell student hops a freight train one evening that turns out to carry a most unusual form of freight.

It’s a circus train, and with his animal skills, along with his animal magnetism, our hero finds a place for himself in the cash-strapped Benzini Bros. company. Much of “Water for Elephants” unfolds in one train car or another, or in the open fields nearby, where the big top rises and falls and the striptease artists do their thing not far from the aerialists, before it’s on to the next town. The Benzini crew’s mercurial, sadistic ringleader, played by Christoph Waltz of “Inglourious Basterds,” is married to star attraction Marlena, played by Reese Witherspoon, whose horse act is soon replaced by an elephant act. Her co-star is the pachyderm who wins Jacob’s heart while enduring the cruelties inflicted by Waltz’s August (not easy to watch, even if you know the American Humane Association was all over this one). The elephant also wraps up the plot, which canvasses everything from a tastefully smoldering romance between Jacob and Marlena to a climactic stampede.

Corny, right? We’re back in the arena of Cecil B. DeMille’s “The Greatest Show on Earth” (1952), or — in the late silent era — the now-lost F.W. Murnau circus story “4 Devils” (1928). That one began with title cards reading: “Step inside, folks! You come to laugh. And to be thrilled — but do you know at what a cost to those who entertain you?” While “Water for Elephants” is softer and more sentimental, the material requires utter commitment and belief in the power of the corn.

The ringer here is screenwriter Richard LaGravenese, who helped make a very good film out of the world’s worst romance novel (“The Bridges of Madison County”). With “Water for Elephants” he has compressed the events very shrewdly without turning them into a manic “Perils of Marlena” serial. The female protagonist remains somewhat passive, as she was on the page, which can be frustrating. Waltz’s archetypal villain cannot help but steal focus when he’s on-screen, partly because of the abuse of which the character is capable, partly because Waltz is just so damned interesting to watch.

That’s more than can be said for Pattinson, who is easy to take without having yet made a single surprising or provocative choice as an actor. Yet he, too, is at least in there working his two or three notes hard, and often effectively. The director, Francis Lawrence (“I Am Legend”), relies mainly on his artistic collaborators, notably production designer Jack Fisk and cinematographer Rodrigo Prieto, to create and sustain the atmosphere. The digital effects never overwhelm things. Moving both the camera and the bodies within the frame, Lawrence is more efficient than inspired at this point in his career, but he does show solid instincts in letting actors interact within the frame.

With his fierce emotional zigzags, Waltz keeps Pattinson and Witherspoon (who retains immense audience appeal) on their toes. Hal Holbrook appears in the bookend sequences, where we see old Jacob remembering back to the events of ’31. The scenes recall “The Notebook,” “Madison County” and a hundred other bars of soap.

It’s a testament to the general effectiveness of “Water for Elephants” that you don’t watch it and mentally check-mark these precedents. I went with it. I was happy to go with it. The movie works, and it’s only unexpectedly good because 20th Century Fox waited until the last minute to screen it for review.