Though it might literally be appropriate to describe a film about a woman’s thousand-mile walk to self-discovery, the word “pedestrian” is not one its makers would probably appreciate being used with reference to their adaptation of Cheryl Strayed’s much-praised 2012 bestseller. Unfortunately, it’s a pretty accurate thumbnail critique of Jean-Marc Vallee’s “Wild,” a disappointing follow-up to his electrifying “Dallas Buyers Club.”

That film—another fact-based tale—was of course buoyed by the performances of Matthew McConaughey and Jared Leto, both of whom deservedly took home Oscars for their work. “Wild” has a strong lead as well in Reese Witherspoon, whose dedication to the role of Strayed is obvious in every frame. But good as she is, Vallee’s film pales in comparison to another about a female hiker, John Curran’s “Tracks,” in which, it must be said, Mia Wasikowska also outdistances Witherspoon in virtually every respect.

Strayed (Witherspoon)—nee Nyland—is introduced in mid-hike, as she removes a boot to examine her injured foot, loses it down a cliff, and then angrily hurls the other after it, an indication she still has a way to go to recover her emotional equilibrium. It then takes us back to the beginning of her 1995 effort to complete a 1,100-mile journey along the Pacific Crest Trail from the Mojave Desert to the Washington-Oregon border, starting with a send-off from supportive ex-husband Paul (Thomas Sadoski) and a struggle to come to terms with an overstuffed backpack (an amusingly slapstick scene). Only later will the film explain, in a series of flashbacks, why she’s putting herself through the ordeal: her beloved mom Bobbi (Laura Dern), a single parent struggling to support Cheryl and younger brother Leif (Keene McRae) while also going back to school herself, died of cancer in 1991. That sent the girl into a downward spiral of infidelity and drug use. The hike was, in effect, a part of her recovery—and redemption.

This is the sort of uplifting story of successful self-help that makes for a great read, and it’s understandable that the book became such an overwhelming success. With the magnificent scenery as an added element, it would also seem a natural for the screen, especially with Witherspoon committed to the project as producer as well as star.

In the event, however, the result is mixed. Witherspoon is very good, exuding determination while also conveying Strayed’s self-doubt (understandable given the circumstances of the adventure) and sense of vulnerability as a woman alone in an environment in which she’s liable to encounter men who might be a threat (understandable given her own checkered past). Yves Berlanger’s cinematography is also impressive, capturing the beauty of the locations in widescreen images that are often lovingly composed.

But the comparison to “Tracks,” and going even further back to Danny Boyle’s “127 Hours,” points up some unhappy weaknesses. If Robyn Davidson’s motivation in Curran’s film remained opaque, giving her journey a sense of transcendent mystery, as presented here Strayed’s becomes all too obvious. The flashback montages are theoretically a good idea, since they allow the information to be doled out in bits and pieces. They also feature an excellent performance by Laura Dern as Cheryl’s devoted mom. But they’re not very imaginatively done, and in the end they come to feel heavy-handed, even soap-operatic.

The other problem involves the film’s failure to give us a palpable sense of the solitude that Cheryl’s trek was designed to bring her. Isolation was a fundamental part of the drama in “127 Hours,” and it was very effectively managed in “Tracks” as well. But in “Wild,” it’s relatively rare; in fact, one might think that Vallee is afraid of footage that goes on too long without some other character intruding into the action. That’s not the case simply with the flashbacks, but with the rest of the film as well. Five minutes hardly go by without Strayed bumping into someone in the wilderness, whether it be the farmer who takes her home for a meal and a shower, or the fellow hiker she spies after a dip in a river, or the journalist who mistakes her for a hobo (another welcome dose of humor), or the hunters who take an unhealthy interest in her, or the grandmother and child she comes upon on a trail, or the female hiker she commiserates with, or the ranger who wants to share a drink with her, or the three college types she does drink with. The inclination to add somebody, anybody else to Strayed’s story—when a human is lacking, some animal will do, even if it’s a rattlesnake—suggests that she wasn’t really very far from civilization and her ordeal not all that extraordinarily.

Still, like “Gone Girl” before it, “Wild” has a built-in fan base, and they’ll doubtlessly come out for it. The book’s admirers may find, though, that Cheryl Strayed’s ordeal was more powerful on the page than it turns out to be on the screen.