Three of the most talked-about movies of the season are based on best-selling books. But are the movies faithful to the authors' work?

"The Chronicles of Narnia: The Lion, the Witch and the Wardrobe"

BASED ON

"The Lion, the Witch and the Wardrobe," one of the seven books in C.S. Lewis' The Chronicles of Narnia series.

PLOT

The four Pevensie children step through a wardrobe into the magical land of Narnia, where they help the great lion king, Aslan, defeat the White Witch and free the Narnians from oppression.

DIFFERENCE BETWEEN MOVIE AND BOOK

Producer Mark Johnson insists the movie is "incredibly faithful to the book. ... certainly the spirit of the book." But some things, he says, have been added and changed. "There is an action sequence as the kids are making their way to Aslan's camp that is not in the book that we felt the movie needed," he says, citing one of several examples. And secondary characters — Susan, the older sister, for example — are fleshed out in the movie, "to give everyone more life."

"MEMOIRS OF A GEISHA"

BASED ON

"Memoirs of a Geisha" by Arthur Golden

PLOT

A poor, young girl works as a servant in a geisha house. Under the tutelage of the geisha Mameha, she grows up to be a famous geisha prized for her beauty and talents.

DIFFERENCE BETWEEN MOVIE AND BOOK

"It really is precisely the novel that I wrote transformed onto the screen," Golden says. Well, not that precisely. He cites a few "very small changes." In the book, Sayuri's mizuage (virginity) is sold to Dr. Crab, the highest bidder. Not so in the movie, where the highest bidder is someone else, and the transaction is a bit more complicated. And at the end of the novel, Sayuri seduces a Japanese character for her own purposes. In the movie, he's a Westerner.

"BROKEBACK MOUNTAIN"

BASED ON

Annie Proulx's 1999 short story "Brokeback Mountain," part of her collection "Close Range."

PLOT

Ranch hands Ennis del Mar and Jack Twist meet and fall in love one summer while working as a sheepherder and camp tender. They part ways, marry and father children, but intermittently reunite. Their love needs to survive society's intolerance of gay relationships.

DIFFERENCE BETWEEN MOVIE AND BOOK

Larry McMurtry and Diana Ossana, who wrote the script, "used the whole short story but had to really extrapolate from there," says James Schamus of Focus Features, distributor of the film. Proulx's original work is "such a perfect exemplar of short story. Sometimes in one sentence she describes something that takes 10 scenes to cover in the film. But the movie is still her version."