Alan Moore has written a number of excellent, cerebral graphic novels that have been turned into awful, mindless movies:
In Hollywood you’re going to have the producers and the backers putting in their … well, I don’t want to dignify them by calling them ideas, but … having their input, shall we say. You’re going to get actors who’ll say they don’t want to say this line or play this character like that. I mean the police inspector in From Hell, Fred Abberline, was based on real life: He was an unassuming man in middle age who was not a heavy drinker and who, as far as I know, remained faithful to his wife throughout his entire life. Johnny Depp saw fit to play this character as an absinthe-swilling, opium-den-frequenting dandy with a haircut that, in the Metropolitan Police force in 1888, would have gotten him beaten up by the other officers.
On the other hand when I have got an opium-addicted character, in Allan Quatermain [in The League of Extraordinary Gentlemen], this was true to the [original] character — he showed a fondness for drugs on several occasions. But Sean Connery didn’t want to play him as a drug-addled individual. So the main part of Quatermain’s character was thrown out the window on the whim of an actor. I don’t have these problems in comics.
Naturally, he’s not happy with V for Vendetta:
I’ve read the screenplay, so I know exactly what they’re doing with it, and I’m not going to be going to see it. When I wrote “V,” politics were taking a serious turn for the worse over here. We’d had [Conservative Party Prime Minister] Margaret Thatcher in for two or three years, we’d had anti-Thatcher riots, we’d got the National Front and the right wing making serious advances. “V for Vendetta” was specifically about things like fascism and anarchy.
Those words, “fascism” and “anarchy,” occur nowhere in the film. It’s been turned into a Bush-era parable by people too timid to set a political satire in their own country. In my original story there had been a limited nuclear war, which had isolated Britain, caused a lot of chaos and a collapse of government, and a fascist totalitarian dictatorship had sprung up. Now, in the film, you’ve got a sinister group of right-wing figures — not fascists, but you know that they’re bad guys — and what they have done is manufactured a bio-terror weapon in secret, so that they can fake a massive terrorist incident to get everybody on their side, so that they can pursue their right-wing agenda. It’s a thwarted and frustrated and perhaps largely impotent American liberal fantasy of someone with American liberal values [standing up] against a state run by neo-conservatives — which is not what V for Vendetta was about. It was about fascism, it was about anarchy, it was about [England]. The intent of the film is nothing like the intent of the book as I wrote it. And if the Wachowski brothers had felt moved to protest the way things were going in America, then wouldn’t it have been more direct to do what I’d done and set a risky political narrative sometime in the near future that was obviously talking about the things going on today?