Lonesome Dove. They made it into a mini series, which is the only way it could have been properly accomplished. I would say that both are on equal footing.
The obvious answer: The Lord of the Rings. I mean, can anyone name any other movie that was arguably better than the book? (or at least more likable). From the meticulous attention to detail, to how true it stays to the books, this epic adaptation stands out as the clear champion among books-to-movies. One movie worth noting is "Adaptation". Charlie Kaufman was commisioned to adapt Susan Orlean's The Orchid Thief to movie, but after dealing with writer's block, instead wrote a script about his difficulty adapting the book to a movie. Also interesting, in the script, he adds a fictitious twin brother, Donald, that was intended to represent the hollywood sell-out side that Charlie is battling. In the actual credits Donald Kaufman, though a fictitious character, is credited for writing the movie alongside Charlie. The credits close with the words, "In loving memory of Donald Kaufman." When the movie was nominated for the 2002 Academy Award for "Best Film Adaptation", both Charlie and Donald were credited as co-writers.
are you asking only for which book that was ever made into a movie was the best book of all books?... or which book made the best movie?
My personal favourite is A Scanner Darkly -- the greatest adaptation of a Philip K. Dick novel I've ever seen. The movie and the book are both overwhelmingly good. Second prize (in terms of adaptation) goes to Kubrick's Lolita if only for the incredible challenges facing him in bringing this story to Hollywood so successfully in the face of The Catholic Legion of Decency and numerous other obstacles.
For me, the best book that was made into a movie was Michael Criton's Eaters of the Dead. It became the movie, The 13th Warrior.
The Day They Gave Babies Away. I have not read the book but I cried and cried through the film. I Remember Mama. is another good one. Both were based on true stories.
Elfriede Jelinek's The Piano Teacher, adapted by Michael Haneke. Such a skilful adaptation given the original text.
I mean, can anyone name any other movie that was arguably better than the book? Yes...The Sound of One Hand Clapping
Indeed - North & South by Elizabeth Gaskell. The romantic conflict between Mr. Thornton and Margaret is better portrayed on the screen than by Gaskell's words.
I don't mention Stephen King very often here, because I'm not really a fan of his, but I thought his "Rita Hayworth and the Shawshank Redemption" was an excellent story, and it was made into "The Shawshank Redemption", which is a masterpiece of a movie. I think the movie is better than the novella, and one of the best movies I've ever seen.
The Lord of the Rings trilogy was amazing. It has my vote. The books were good too, but I agree that the films were better.
A Wrinkle in Time without a doubt. It took the book and made everything better. The characters, the plot. It was so good.
@arron89 -- good call. Haven't read the book, but the movie is amazing. @ojduffelworth -- that's easy. 2001: A Space Odyssey
Lord of the Rings is a good bet, like many said. While I can't say the film was better than the book per se, it was definitely accessible to the average person (as Tolkien's writing can get pretty... well... difficult, at least for me, at times) and adapted the story well. However, thinking about it a bit, I think one movie adaptation I found particularly powerful was Grave of the Fireflies, which has been oft cited as one of the few anime movies that is well-known and highly praised among Western movie critics (or something like that). I never read the original semi-autobiographical novel, but the movie was one of the few movies that made me cry, so I'm pretty sure the novel must have been pretty good, too.
I despise the Godfather movies but recognise that many think them meritorious...aren't they based on a rather middling Mario Puzo (is it?) book(s)?
The lord of the rings, in my opinion. Even nowadays I like the movies but I remember that the first time I watched them I was totally "WOW"