The Best Adapted Screenplay category is always the more crowded and competitive of the Oscar writing categories, but this year it feels as if the contenders should be judged the same way diving competitions are: with one score for how artful the film is, the other for the degree of difficulty.

If that were the case, those D.D. scores would be off the charts for a few of this year's adaptations, because a number of the year's most notable films come from books that seem all but unfilmable.

In fact, "Cloud Atlas" author David Mitchell has used exactly that word, unfilmable, to describe his 550-page novel, which tells six different stories from six different eras in a mirror-image construction that begins in the 19th century, progresses to the distant future, then reverses course and ends on the same story with which it began.

But Andy and Lana Wachowski and Tom Tykwer, holed up in a rented Costa Rican house, turned those stories into color-coded index cards and rearranged them in countless ways until they figured out how to turn that unfilmable novel into an enormous, messy, exhilarating film, with help from the likes of Tom Hanks and Halle Berry (above) in multiple roles.

"Lincoln" screenwriter Tony Kusher took Doris Keans Goodwin's "Team of Rivals" -- a book about Abraham Lincoln in which less than five pages deal with the passage of the 13th Amendment -- and turned it into a two-and-a-half hour film about that legislative struggle.

Peter Jackson, Fran Walsh, Philippa Boyens and Guillermo del Toro started with "The Hobbit," a 300-page children's book, and somehow pumped it up into a three-part big-budget extravaganza à la the "Lord of the Rings" trilogy, another three-part Jackson epic based on a far meatier book.

And Tom Stoppard wrestled the 800-plus pages of "Anna Karenina" into a script sturdy enough to withstand director Joe Wright's last-minute decision to stage the whole thing in a decrepit theater, while John McLaughlin took a non-fiction book about the making of Alfred Hitchcock's "Psycho" and turned it into an entertaining yarn leagues removed from the style of the original.

A few more case studies from a year of high degree-of-difficulty adaptations:

SLICE OF "PI"

When David Magee first read "Life of Pi," he was working on "Finding Neverland" with director Mark Forster. He recommended the book to Forster but had a ready answer when the director asked if it would make a good film: No, it's too difficult to adapt. "It's a great book," he thought. "But I don't think it's a movie."

"And I really didn't give it much more thought than that," said Magee, who worried that the novel had insurmountable story obstacles, as well as the technical challenge of putting a boy and a tiger together in a lifeboat.

A decade later, with CG imagery improved to the point where the film was technically possible, Magee tackled the novel with director Lee. "The first act particularly took a long time," he said of the section in the novel in which the character of Pi tells the story of his childhood. "We were eliminating characters, we were combining characters, and a lot of the challenge was finding the right tone for that first act so that you didn't feel like you were sitting down to a class in comparative religion.

"For several months I tried different structures, different rhythms, and it wasn't until Ang and I went on a research trip to India, which is a fantastical place, that Ang said to me, 'It's kind of like an adult telling a great yarn, a great children's adventure story.' We had been dancing around that idea for weeks, but when he said it that time it registered to me, and I started writing the first monologue while we were driving."

Then there was the second act. It took countless drafts for Magee and Lee to crack the challenge of finding the appropriate tone, figuring out what to do with a long act in which the main character is adrift on a boat with only a Bengal tiger named Richard Parker as a companion.

Magee said he tried to use as little dialogue as possible to emphasize its stark difference from the third act, which he said "is very much spoken ... and in some ways calls into question everything that preceded it. "We tried to contrast it as much as possible, so it felt like two different stories. You had to decide: Do you believe the visual story you experienced, or the story you're told?"

"ROAD" TRIP

"I think I might have been the eighth writer that had been hired to do an adaptation of 'On the Road,'" Jose Rivera told TheWrap. But unlike the first seven -- which included Francis Ford Coppola and his son Roman, as well as Michael Herr, Barry Gifford and Russell Banks -- Rivera's version actually made it to the screen, in a film directed by Walter Salles and starring Garrett Hedlund, Kristen Stewart and Sam Riley.

"It's was a tough one, because 'On the Road' is a novel full of digressions and subplots and secondary characters, including some very one-dimensional women characters," said Rivera, a playwright whose previous film was Salles' "The Motorcycle Diaries."

"But I had a couple of advantages. One was I wasn't one of those people whose life was changed by the book. So I wasn't in thrall to the book, and I wasn't treating it like sacred territory. In a way, I treated it almost like a standard buddy film about two men on the road, as opposed to kind of worshipping the icons that were the beat writers."

Rivera and Salles made a point of adapting the original, "scroll version" of "On the Road," which he said is "far edgier and sexier" than the bowdlerized version that was initially published. But he still had to find a movie-friendly structure in a book that really didn't have one—so he focused on a section in which the main characters, Dean Moriarty and Sal Paradise, spend some debauched time south of the border.

"Everything accelerated in that section,” he told TheWrap. “They go crazier, and it's also the biggest crisis of their friendship. So when I read the Mexico section I thought, that needs to be the third act, and we'll just build the other two acts around that."

Still, he admitted, it took about 40 drafts to structure the screenplay—and even after the film's Cannes debut, Salles went back to re-edit the film and remove a number of scenes, many of which were improvisations that had not been in Rivera's script.

FOUR'S A CROWD
Ronald Harwood learned that the theater and the cinema are vastly different mediums the first time he adapted one of his plays to the big screen. The play was "The Dresser," a 1980 drama that was turned into a 1983 movie and for which he received an Oscar nomination. He adapted it almost intact, and later had an enlightening encounter with director Billy Wilder.

"He said to me, 'That film of yours, 'The Dresser,' it's a terrible film," Harwood told TheWrap. "'I should know, I've seen it six times.' It was the greatest compliment I've ever been paid. And he was right."

Theater, Harwood said he has since learned, "is an entirely different way of telling a story. The theater is a medium of language: Words matter in the theater. In the movies the images matter, it's self-evident. So you have to abandon the play, in a way, but try and preserve the heart of it. Your instinct might be to use as much as possible of the original play, but I think it should be to use as little as possible, in terms of dialogue and that."

For "Quartet," that meant losing the opening of the play, which he called "one of my favorite openings to anything I've ever written." In the play, the action begins in a home for elderly musicians, with one aging but randy opera singer watching a former diva who can't hear him because she has headphones on. "May I tell you, Cissy," he announces, "that you have the most beautiful tits I've ever seen."

"I loved that line, and it got a huge laugh wherever it's been played," Harwood said. "It's still in the film, but we couldn't open with that, unfortunately. We had to set it up differently."