Nicholas Sparks strikes again with “The Longest Ride,” a movie that replays many of the writer’s familiar romantic-tragic tropes but situates them in a rodeo milieu. Aficionados of the saccharine Sparks formula may applaud; everyone else is advised to set off in the opposite direction and get as far away as possible, especially because under George Tillman Jr.’s desultory direction the treacle flows for well over two hours, an interminable serving of the author’s trademark schmaltz.

Scott Eastwood, son of Clint, plays Luke Collins, a North Carolina bull rider who’s seriously injured when thrown and gored by a nasty piece of work called Rango (an animal that actually gets co-starring billing “as himself,” which the beast probably deserves on the basis of flaring nostrils alone). After a year on the mend, he ventures back to the rodeo, appearing for the first time since the traumatic experience on the very night that pretty Sophia Danko (Britt Robertson), a Wake Forest art history senior, has been persuaded to don cowboy boots and attend the spectacle before her imminent departure for a gallery internship in NYC. Naturally the two meet cute—Luke presenting her with his hat after a successful ride—and they get together for dinner, a picnic on a lake that Luke’s prepared as a special treat. On the drive back to campus during a thunderstorm, they come upon a car crash and rescue the elderly driver (Alan Alda) just before the vehicle explodes. Sophia also saves a box of papers from the back seat.

That episode sets up one of Sparks’ favorite narrative tricks—the dovetailing of two romances separated in time, or alternately of lovers separated by time until reunited. That box consists of letters the old man, Ira Levinson, wrote to his beloved Ruth, not only while he was away to serve in World War II, but even—as he tells us—while they were together. (A curious practice, indeed, which seems just a clumsy device to keep the plot going. And, of course, there are no replies.) The story emerges as Sophia reads the letters to Ira while he recuperates: Ruth Pfeffer (Oona Chaplin) was a refugee from Austria who came to Greenville, North Carolina, with her parents in the late thirties. Ira (Jack Huston) fell for her at first sight, and they were soon in love and married though they were very different, he the shy son of a modest haberdasher, she a vivacious lover of the modern art championed at Black Mountain College (where Robert De Niro, Sr., the subject of the recent documentary “Remembering the Artist,” studied).

But of course there was a thorn in the rose of their romance. Ruth desperately wanted a large family, but Ira returned from the battlefield no longer able to sire children as a result of a wound he’d suffered rescuing a fallen comrade. Ruth, a teacher, became a surrogate mother to many of her elementary school students, especially a disadvantaged orphan named Danny (whom they tried unsuccessfully to adopt), but her pain was never fully healed. Still they remained together until her death, and over the years collected a houseful of paintings that remain in Ira’s attic.

The tale of the Levinsons is juxtaposed, of course, with the ups and downs in the relationship between Sophia and Luke as he continues to ride against doctor’s orders (and the wishes of his widowed mother, played by Lolita Davidovich), and their future together is imperiled by her imminent departure for New York and Luke’s inability to appreciate the abstract paintings she so loves. The fact that they’re from “two different worlds” (a cliché actually used here) seems an unbridgeable obstacle until Ira intervenes from the grave, much as Gerald McRaney’s Tuck did in the last Sparks adaptation, “The Best of Me.” That leads to one of the most ludicrous happy endings in all of cinematic history, set at an auction of Ruth’s collection of paintings; but it’s already been preceded by a gruesomely cloying turn involving a reconnection with Danny after many decades have passed. Taken together, the surprises that Sparks and his adapter Craig Bolotin dish out in the final reel will either make you tear up or cause you to snicker in disdain.

Throughout this orgy of crassly manipulative mawkishness, Alda actually tries to act, but is defeated by the banalities put into Ira’s mouth, while Robertson and Eastwood mostly coast by on their good looks and Huston goes the dewy-eyed, sad-faced route. The outlier is Chaplin, whose exaggerated energy is meant, one supposes, to be endearingly intense but more often comes across as positively unhinged. Apart from Davidovich, who’s admirably understated, the supporting cast tends to play to the rafters. The technical side of things is par for the course, with cinematography by David Tattersall that gives everything a beatific glow, and the images are positively drenched in Mark Isham’s sappy score.

Despite the fact that “The Best of Me” tanked (deservedly, it must be said), Sparks has a devoted fan base that could come out for “The Longest Ride” and actually enjoy it. But to the rest of us, it’s just one more hot, heaping Sparksian helping of what the redoubtable Rango undoubtedly leaves in his wake all the time.