Don't listen to Hollywood cynics who are dismissing Billy Bob Thornton's western, All The Pretty Horses, as a kind of The Hi-Lo Country. Stephen Frears' 1998 failure may have also co-starred Penelope Cruz, but further comparison is vastly unfair. While Pretty Horses is not an exciting epic or even a forceful rendition of Cormac McCarthy's cherished novel, it has sufficient merits to warrant a serious look - and a visit to your cinema. An inauspicious American opening, however, is likely to repeat itself in most foreign markets, where westerns with no name casts and art-house epics usually face tough commercial prospects.

A protracted, well-publicised post-production forced Miramax to share expenses with Sony (which is releasing internationally) and to repeatedly reschedule the film's opening. As always, the delays brewed nasty rumours, primary of which was that Thornton couldn't trim his three-hour-plus cut down to a releasable length. The running time is 117 minutes.

As it stands now, Pretty Horses is a problematic, flawed film, one that's easier to evaluate by its intent rather than execution. What went wrong' For starters, Pretty Horses, the first volume of McCarthy's Border Trilogy, has developed a loyal, passionate following. Fans of the novel have complained all along about the casting of Matt Damon as John Grady Cole, the last, vagabond cowboy in a long line of Texas ranchers. The role was first assigned to Leonardo DiCaprio (whose $15m price-tag was too high), then to Brad Pitt, who was also too demanding.

The film is meant to be a sweeping odyssey about a young man's encounters with love, revenge and survival - in other words, another classic coming-of-age Americana. It's post-World War II, and the beloved Texas land where Cole grew up has been altered by highways bisecting the plains and a new way of life that sneers at the traditions of honour.

Upon the divorce of his parents, his grandfather's death, and the loss of his inheritance, Cole sets out in search of a new life. He knows that to fulfil his fantasy, he needs to head for a place where cowboy dreams still exist. He rounds up his pal, Lacey Rawlins (Henry Thomas), and sets off for the Rio Grande, a place free of highways, fences and civilisation, where horses still run wild. As they make their way towards the Rio Grande - the mythic land of John Ford-John Wayne westerns - they cross paths with a volatile misfit (Lucas Black), an encounter that precipitates troubles with the Mexican law.

The love interest is provided by Alejandra (Cruz), the beautiful daughter of a wealthy Mexican landowner who's raised by her feisty aunt. An inner-directed man in the manner of all American cowboys - remember Cooper's motto, a man's got to do what a man's got to do - Cole follows his heart's wild dictate and pursues her.

At its core, McCarthy's tale was an examination of a young man's maturation amidst a harsh, fast-changing world. As an elegiac tale of dispossession, it centred on a boy who loses not only his home and family, but also his dream. Cole's expansive, evocative transformation was conveyed in the book in intense, heart-wrenching terms. Employing voice-over narration, Ted Tally's script captures the essence of the novel's visceral language, its spare and poetic monologues, delivered in a raw, unpunctuated but soaring mode.

Thornton showed talent in directing the intense, intimately-scaled Sling Blade, but he strains in translating the book to an epic western a la George Stevens' Giant, which was based on Edna Ferber's sprawling novel and also dealt with two generations of Texan ranchers. Thornton seems unable to find a satisfyingly visual manner in which to dramatise Cole's odyssey from innocence to experience, from childish games to jeopardising his life for love, from primal revenge to acting with honour - and paying a heavy price for that honour.

Watching this fractured, often lethargic saga, you find yourself craving for a sweeping John Ford shot of the awesome landscape, for the insightful physical observation that made Giant a lyrical masterpiece. Thornton gets the intimate details and relationships all right, but misses on the epic scale, on showing the impact of the raw physicality of the land - the Mexican badlands - on Cole's persona. In the director's defence, the film's lack of a consistent visual style could be a function of the extensive cuts.

Just as intriguing in the book, but again missing from the film, was the theme of a boy searching for approval and support with no parental figure to turn to. This is rendered by McCarthy through brief but powerful encounters between Cole and male figures of authority: the hacienda's boss, the judge who hears Cole's confession and absolves him of guilt. There's a wonderful moment in the novel in which an imaginary character appears in the hall when Cole places a painful phone call to Alejandra. It's a surreal moment in which Cole imagines the stranger to be tap-dancing, but Thornton is incapable of registering it on screen.

Finally, the acting itself is not entirely pleasing. Damon, still exuding boyish charisma, is adequate but no more. The beautiful Cruz, so vivid in her Spanish films, is pallid, and the lack of chemistry with Damon makes their erotic scenes awkward. A large gallery of talented supporting actors, including Bruce Dern as the judge, Ruben Blades as Rocha and Julio Oscar Mechoso as the captain, play too minor roles to be memorable.

Prod cos: Miramax Films/Columbia Pictures; US dist: Miramax Films; Int'l dist: Columbia TriStar; Prods: Robert Salerno, Billy Bob Thornton; Scr: Ted Tally, from a novel by Cormac McCarthy; Cinematographer: Barry Markowitz; Prod des: Clark Hunter; Ed: Sally Menke; Music: Marty Stuart; Main cast: Matt Damon, Henry Thomas, Lucas Black, Penelope Cruz, Ruben Blades