Tricky task translating Dahl to film

For a lot of kids, their introduction to dark comedy is through the twisted stories of Roald Dahl. His books introduced filthy monsters and draconian authority figures in all their grotesque glory, then set good-hearted (if mischievous) child protagonists on them.

A live-action version of Dahl's 1982 book The BFG makes its way to the screen next month, directed by Steven Spielberg. The movie stars Mark Rylance as the titular dream-catching Big Friendly Giant, with Ruby Barnhill playing his new best friend, plucky orphan Sophie.

Although most adaptations of Dahl's works have turned out pretty well, The BFG shows how tricky the move can be.

The movie is vividly imaginative, with breathtaking special effects that transform Rylance into a beanpole of a supersized human. It revels in Dahl's extensive vocabulary of made-up words, such as hippodumplings and crocadowndillies. The movie also features the irreverent stuff Dahl loved so much, like earth-quaking flatulence.

But it isn't nearly as exciting as the book. The movie spends much more time acquainting us with the world of giants than taking advantage of the action these massive, bloodthirsty characters are capable of scaring up.

It could have learned some lessons from previous Dahl adaptations. Here are a few.

Don't worry about what the author thinks

Willy Wonka & the Chocolate Factory (1971)

Plot in a sentence: The impoverished young Charlie Bucket wins the chance to tour an eccentric's workshop and watches as ill-behaved kids get their comeuppance.

Dahl was famously disgusted with the movie version of his 1964 book, directed by Mel Stuart. The screenplay Dahl wrote was heavily reworked, but that wasn't his only gripe: He wanted Spike Milligan to play Willy, and he thought Gene Wilder's wonky Wonka overshadowed Charlie's role. (The title of the movie was even changed from the book's alliterative Charlie and the Chocolate Factory).

Audiences weren't much easier to please; the movie was met with a disappointing box office upon its release. But a few years down the line, it became hugely popular. And why is that? It really did capture some of Dahl's spirit. For one, it didn't soften the content for kids, leaving the scare factor high. That eerie boat ride was enough to give children nightmares well into adulthood. It also appealed to parents as much as their offspring, which was a hallmark of Dahl's work.

Another adaptation of the novel - this time retaining the book's title - came out in 2005, courtesy of Tim Burton. Dahl fans agreed the writer, who died in 1990, would have been happier with this incarnation, which more closely followed the book. But audiences might have been too distracted by Johnny Depp's soft-spoken, giggling, creepy Wonka to fully appreciate the story.

Gore preferred, either shown or implied

The Witches (1990)

Plot in a sentence: The recently orphaned Luke Eveshim goes on a trip with his grandmother and must battle hideous witches after they turn him into a mouse.

Here was another adaptation that Dahl disavowed. (He wasn't easy to please.) And yet, the movie lived up to the scary spirit of its source material. It's basically a horror movie: The witches are sickening to look at (thanks to fine special effects by Jim Henson), and they do ghastly things to children - luring them in with sweets, then transforming them into rodents. In one particularly nightmarish scene, a cook lops off poor Luke's tail.

The Grand High Witch is a perfectly cast Anjelica Huston.

The most conspicuous change from the book is Luke ends up in the film as a boy again. Even Dahl can't come between Hollywood and its happy endings.

No need for kid gloves

Matilda (1996)

Plot in a sentence: Wunderkind Matilda Wormwood uses her telekinetic powers to trounce her brutal headmistress, Miss Trunchbull.

Danny DeVito directed this adaptation of Dahl's 1988 novel. It turned out that the man behind Throw Momma From the Train and The War of the Roses was the perfect person to usher the dark children's story to the screen.

"Sit down, you squirming worm of vomit!" the militaristic Trunchbull tells a student at one point. Later, she grabs a girl by the pigtails and hurls her across a yard. Matilda isn't as scary as The Witches, but it's just as disturbing at times, with Matilda's life at home being as soulless as her time at school. Her father (DeVito) rips up her library books and forces her to watch idiotic game shows. Aside from transferring the action from England to the States, DeVito stuck quite close to the original.

If you have your own crazy idea, go with it

Fantastic Mr. Fox (2009)

Plot in a sentence: An impish fox has to recruit help after his chicken-thieving makes his family and friends the target of three dangerous farmers.

Wes Anderson went in an entirely different direction with his stop-motion animation version of Dahl's 1970 novel. The contours of the story are the same, but Anderson took liberties with a lot of details. Even as the movie is a work of its auteur, it's also faithful to Dahl's spirit, with wry comedy and an insistence on not looking down on its youngest audience members.

"You cussing with me?" Mr Fox (George Clooney) asks a badger (Bill Murray) he's sparring with. "Don't cuss with me you little cuss," the badger responds. The dialogue is PG, but with a naughty streak.

There are still hints of gore but also plenty of heart. Would Dahl have approved of the director's almost pathological devotion to whimsy? Maybe not. But that doesn't mean we can't enjoy it.