Lee Child's Reacher novels have become a sure-fire way of making a long trip seem shorter. Their muscular prose and fast-moving plots are nothing if not attention-grabbing, and they bring an Old Testament sensibility to the adventures of the former military policeman-turned-crime fighter as he makes his way across America.

The first film adaptation of the series Jack Reacher, which opens in Australia next week, finds Cruise embarking on a projected franchise that the filmmakers hope will emulate the success of the Mission Impossible movies. Written and directed by Christopher McQuarrie (who won an Oscar in 1995 for his screenplay for The Usual Suspects and is the writer-director of the forthcoming Mission Impossible 5), it is based on the ninth book in the Reacher series, One Shot. It hits our cinemas in a flurry of controversy over casting that highlights the tricky problem of adapting wildly popular book heroes to the screen.

The first novel in the series, Killing Floor, was published in 1997, and 16 more have followed, their global sales cited as in excess of 60 million. All fetishize Reacher's physique: he's "six five, at least", weighs around 250 pounds, isn't handsome in a conventional way, and carries scars on his torso that testify that he's a man unafraid to put his body on the line. Women find him irresistible and men want to be him. The British-born, New York-based Child told Time magazine in 2007: "I would be him if I could get away with it."

As soon as Tom Cruise was anointed to play the title role, the flak began. Since the actor is about 170 centimetres (five feet seven inches), well-groomed, and closer in appearance to a Ken doll than to Child's creation, how could he possibly fit the bill?

Casting against the author's specifications is often lamented by both readers and the writers themselves. After Sean Connery was cast as 007 in Dr No (1962), the book's author, Ian Fleming, is reported to have quipped: "I'm looking for a Commander Bond, not an overgrown stunt man". However, he turned out to be so impressed by the Connery charisma that he adjusted the background of the book Bond to accommodate the actor.

It was this kind of quality, rather than a strict physical likeness, for which McQuarrie acknowledges he was chiefly looking in casting the role, and Child was happy to allow the responsibility to rest on the filmmaker's shoulders.

''When we sat down to compile our list of who were our dream actors for this role,'' says McQuarrie, ''they were all dictated to us by who we thought could best pull off Reacher as a character. That list of names never included anyone to fit the physical type of Jack Reacher. They were all actors we thought were really well-suited to the role, but none was six feet five, with blond hair and blue eyes, 250 pounds. And, in fact, I challenge you to find that actor anywhere." But then Cruise, the film's producer, volunteered his services.

And, against the odds, it turns out size does not matter. The actor's willingness to throw himself into a part is legend. In Mission Impossible - Ghost Protocol (2011), when his character was required to scale the exterior of the Burj Khalifa tower in Dubai - the tallest man-made structure in the world - Cruise, incredibly, declined the use of a stunt double. To prepare for the role of Reacher, he spent four months learning the Keysi fighting method, a form of hand-to-hand combat that uses elbows, knees and weight leverage, and provides ways of fighting several opponents. The actor does all his own stunts in the film, including a hair-raising car chase that is not in the book, and was shot without the use of green screen (a background that allows the later incorporation of special effects).

Five minutes into Jack Reacher, I doubt that anyone will be thinking about the physical differences between the Reacher on the page and the one on the screen.

Getting the casting of the main character right is one thing, but there's much more than that to a successful adaptation. What the process also involves is finding visual equivalents to the way a novel shapes a story and creates a point of view, sometimes moving beyond the narrative parameters established by the original.

The literary Reacher is not only a master detective in his ability to link details that no one else pays any attention to, but a man without peer in hand-to-hand combat - an irresistible force of nature. Even though Child writes the novels in the omniscient third person, he underlines Reacher's almost superhuman powers by having him explain to us beforehand exactly how any given situation is going to unfold.

Confronted by a group of thugs bent on his demise in One Shot, he outlines at length and in great detail exactly how he is going to deal with them. And you never doubt for a minute - rightly - that that is exactly what he's going to do.

McQuarrie, though, wants his version of the character to be more vulnerable. "I'm so exhausted by superhero movies," he says. "Reacher's not super, he's just a hero. And, in fact, isn't even that. I take very seriously that scene in the film where he says to Helen (Rosamund Pyke) on the phone, 'You think I'm a hero? I'm not a hero'.''

In the film's depiction of the same fight scene, McQuarrie has Reacher explain to the thugs what he's about to do to their various body parts with the precision of a scientist. But instead of placing us inside the safety zone of Reacher's point of view during the ensuing confrontation, McQuarrie works to sustain the possibility that it could all go wrong.

Eschewing the immersive, hand-held chaos now conventionally used by filmmakers in action sequences (as in the Bourne film series, based on the Robert Ludlum books), he keeps the camera at a distance, taking up the point of view of an outside observer. In contrast to the book's story-telling strategies, the cinematic effect is to keep the outcome uncertain.

There are other literary-cinematic precedents invoked, as well. Child has described the character as "the descendant of a very ancient tradition: the noble loner, the knight errant, the mysterious stranger who has shown up in stories forever". McQuarrie says that while he did not realise it as he was shooting the film, "what I was essentially doing was making a modern version of The Man with No Name stories'' and other Westerns. As we're talking, he realises that the film's final sequence contains an unconscious echo of one of them, connecting "the moment of Reacher on the bus to Shane on his horse" in the 1953 Alan Ladd movie of the same name.

He reveals the process of bringing Reacher to the screen even determined the selection of the ninth book in the series as the one from which to try to launch the franchise.

"The first book, Killing Floor, starts after the story has already begun," he says. "You meet Reacher sitting in a diner. He's arrested and he's playing catch-up, and, in the process, he's explaining to people who he is and how he lives his life. So while, to the reader, that's an interesting introduction, cinematically it's very static. It's Reacher sitting in a room and 'telling' as opposed to 'showing'.

"Whereas, in One Shot, the story starts before Reacher makes his entrance. His name is brought up before we've ever met him. People are searching for him and, in the process, telling the audience who he is and how he lives his life. It's a much more cinematic and a much more mythic introduction to that character.

''And, if you look at all 17 books, it's the only one that introduces the character that way. So, in that respect, it was almost dictated to us which book was the best introduction."

The box office will decide whether or not McQuarrie's film will lead to a series. He's certainly looking forward to the possibility: "Now that I've established the character and am not obligated to lay out so much exposition in terms of learning who he is, now that the audience would presumably be familiar with who he is, I can make a much smaller, more spare movie that's still going to feel big.''

Whatever happens in the market, Jack Reacher is a reminder that there are no rules that require filmmakers to use words on a page as sacred texts or as identikits for casting choices.

It also suggests that it might be time for the naysayers to cut Cruise a bit of slack: his range might be limited, the risks he takes generally physical rather than emotional, but he's an actor who takes his craft very seriously and he deserves respect for the way he walks tall here.

Jack Reacher opens on Thursday.

Crime fighters in waiting

HARRY HOLE A policeman in Oslo, Norway, he’s appeared in nine novels by Norwegian Jo Nesbo, the first, The Bat (1997), set in Sydney. An adaptation of the seventh book, The Snowman, is in development, written by Matthew Michael Carnahan and to be directed by Scorsese.

ANNIKA BENGTZON An investigative journalist for a tabloid in Stockholm, she has featured in eight novels by Swedish author Liza Marklund. In The Bomber (Deadline, 2001) and Paradise (2003), she’s played by Helena Bergstrom.

DETECTIVE CHIEF INSPECTOR DAVID BROCK AND DETECTIVE SERGEANT KATHY KOLLA Whether working separately or together, the Scotland Yard duo at the heart of a dozen novels by Scotland-born, Australia-based Barry Maitland would be ideal material for a TV series.

KINSEY MILLHONE Kentucky-born Sue Grafton has spent a career ushering her private eye through the alphabet. The latest is V is for Vengeance and, while two books were adapted for Japanese TV in the 1980s, none has appeared anywhere else. It’s time. Catherine Keener, Mary McCormack or Holly Hunter would be perfect casting.

SHARON McCONE Michigan-born Marcia Muller nowlives in northern California and has written 30 novels and two shortstory collections featuring her private eye. The latest is Looking for Yesterday. It’s astonishing that none has been adapted.

by TOM RYAN