Many novels have been turned into movies but not vice versa, this mostly takes from the novel more than it gives, even financially a person would buy a ticket rather than buying a book, but any way the authors get millions of dollars so there is no need to worry about them :D.
When a novel is turned into a movie, the movie will have two types of audience: people that read the novel and people who haven't, clearly the second type will be larger that's why the director will try to reach and satisfy them more than the first type, this leads to you watching something totally different from what you expect (in case you are of the unfortunate first type).
I just been to Sherlock Holmes by Robert Downey and Jude Law, the movie is great from the perspective of a person that never read any of Sherlock Holmes cases, but when I recall the cases and the voices (as Sherlock Holmes was presented by the BBC Radio in sixtieth) I see Sherlock Holmes as a man in his late fourties or early fifties, maybe in a good shape but not so athlete, we can say quite fat with a moustache, and as I hear the strong sound of Dr Watson, I see him similar to Sherlock Holmes but little older maybe, and with a full rounded face, a typical gentleman of London in the 19th century, well all this "imagination" of mine might be what Sir Arthur Conan Doyle wanted the reader to say or maybe not, but I am quite sure that while he was writing he never thought of Sherlock and Watson as two men destroying London while they are chasing criminals like the movie put them, actually the movie made them closer to cowboys rather than gentlemen of the 19th living in London, when you read any of the cases, you will rarely see the kind of extensive force and action that existed in the movie.
This surely puts the largest part of the audience in great satisfaction as they watch the two men jump, hit and make jokes, and they will surely enjoy Sherlock's mad acts and expressions, which doesn't match with the cases, maybe he was a little bit "weird" and unorganized but not a lunatic that is closer to insanity than geniosity.
Anyway as the director wants ALL the audience satisfied, he will make up with you be emphasising on details that might not be of importance but they were in the original Sherlock Holmes like: the address of the rooms where Sherlock and Dr.Watson lived which is 221 Baker Street, the names of the landlady "Miss.Hudson" and the detective "Lastrade". These things could have been ignored without disturbing you but the director kept them, just to tell you "hey man don't be upset this is still Sherlock Holmes of Sir Arthur".
I guess the same thing happened with "Angels and Demons" of Dan Brown and "The Twilight Saga" by Stephenie Meyer, on the other hand stories like "Troy" and "300 Spartians" were sent to life again by movies.
So what do you think about novels turning into movies.
Statue of Sherlock Homes in Edinburgh
A Drawing of Sherlock Holmes
Dr.Watson (left) and Holmes (right)
The ALL NEW Holmes and Watson
COOL isn't it? :D :D