If a film had a daemon would it be a bookworm?

A film adaptation has a lot in common with a book review. It is the scriptwriter's take on the book; one man's opinion. Okay, that's a gross simplification perhaps, but bear with me. Actually we'll get round to the bear later.

I read Nineteen Eighty-Four ten years before I saw the film starring John Hurt and it was a few years later I saw the BBC adaptation starring Peter Cushing. The film and the TV drama were very different and yet both were faithful to the book. I was genuinely puzzled and read the book again for, I think, the third time.

I was lucky to see the TV version. The play was adapted by Nigel Neale (best known for his Quatermass series) and the first broadcast caused a furore; questions were even asked in the House about the suitability of such strong material for television. Furious watchdogs campaigned for a second performance planned for a few days later to be cancelled. The BBC's Head of Drama, Michael Barry, refused to concede, and that second live performance was recorded. The rest, as they say, is history.

It's been said we live in a post-literary world. Since the bulk of the information on the internet comes in words, albeit sometimes a strangled version of English, I could dispute that, but I can't argue with the fact that people are reading less books than they used to. I read less books than I used to, but I still watch a bucket load of films. Is that necessarily a bad thing? I don’t think so. Admittedly it's rare that I'll watch a film and then go looking to read the book from which it was adapted, however, if I've enjoyed a particular book, I'm wide open to watching an adaptation of it, if only so I can nitpick over how they should have done it.

At the end of the day a film is a collaborative process no matter how firmly any director clings to the reins, whereas reading is the most solitary of occupations. For example, in my first novel I have a clear picture in my head of the character of Truth. It's a young Paul Nicholas – more Just Good Friends, less Cousin Kevin from Tommy. My wife can't see past Eric Idle in the role purely because I describe his entry as "more like a character from a Monty Python sketch than the angel of death"; since both actors are now far too old to play the part, God alone knows who they would cast if the damn thing ever got filmed. Steve Punt's probably in with a shout.

When I read Ken Kesey's One Flew Over the Cuckoo's Nest I had no real picture in my head of Randall P McMurphy in my head. After the film I couldn't ever see anyone else in the role, he so made it his own. A while ago my daughter went to see Christian Slater play the part on the stage and she said he was so convincing in the part and I can imagine that. The novel was originally dramatised on Broadway beginning in 1963 with Kirk Douglas starring as McMurphy and Gene Wilder as the stuttering Billy Bibbit. That I would liked to have seen.

The book is very different from the film, so much of the book taking place in the head of the 6' 8" tall, 'mute' native American, Chief Bromden, a paranoid schizophrenic, who describes hallucinatory images of an all-powerful, all-seeing bureaucratic 'harvesting machine' designed to foster complete social integration – a combine, that would squelch all individuality and create a compliant society (both within the hospital and in the wider society). Kesey was so incensed by the change in the perspective of the story-telling (away from Chief Bromden's first-person perspective) and other changes in the script that he sued the producers.)

The thing Kesey perhaps forgot is that no sooner has his book landed in the hands of a reader, they will start to interpret or misinterpret his characters, they will cast the characters as they see fit and provide them with accents that aren't quite right, or anywhere near right, and there isn't a damn thing he can do about it. Most film-makers, though, have a degree of integrity. They want to bring "their vision" of the book to the masses and that is all it is, what one man sees in another man's work. Unless you're Quentin Tarantino who not only renamed the airline stewardess at the centre of Elmore Leonard's novel Rum Punch but changed her ethnicity too when he cast legendary blaxploitation star Pam Grier in his adaptation, Jackie Brown.

The last film adaptation I saw was A Scanner Darkly, a book I have read many times and a personal favourite. I went fully expecting to be bitterly disappointed, after all what could possibly live up to my expectations? The thing is I wasn't disappointed, the very opposite. I had always had some problems visualising the world in the book, especially the scramble suits. Now that problem has been solved. It wasn't a perfect film, the end was rushed and it definitely helped to have read the book first but I thoroughly enjoyed the experience.

One of my favourite films is Blade Runner, an adaptation of another of Philip K Dick's novels, Do Android's Dream of Electric Sheep? but the novel is not a favourite. This time I saw the film first and Ridley Scott's interpretation of the material is stunning.

Dick worked closely with the Blade Runner producers until his untimely passing in March 1982. He had this to say about the film:

The purpose of this story as I saw it was that in his job of hunting and killing these replicants, Deckard becomes progressively dehumanized. At the same time, the replicants are being perceived as becoming more human. Finally, Deckard must question what he is doing, and really what is the essential difference between him and them? And, to take it one step further, who is he if there is no real difference?

Seeing Rutger Hauer as Batty just scared me to death, because it was exactly as I had pictured Batty, but more so. I could have picked Sean Young out of a hundred different women as Rachael. She has that look.

Of course Harrison Ford is more like Rick Deckard than I could have even imagined. I mean it is just incredible. It was simply eerie when I first saw the stills of Harrison Ford. I was looking at some stills from the movie and I thought, this character, Deckard, really exists. There was a time that he did not exist; now he actually exists. But he is not the result of any one individual's conception or effort. He is to a very large extent, Harrison Ford's efforts. And there is actually, in some eerie way, a genuine, real, authentic Deckard now.

Friends of mine who looked at the photographs, who read the novel, said, 'Do you realize that if you had not written that book, Harrison Ford would not be wearing that tie, he would not be wearing those shoes?' And I said, 'That is true. But what is more exciting is that if Harrison Ford had not played that role, Deckard would never become an actual person.' Ford radiates this tremendous reality when you see him. And seeing him as a character I created is a stunning and almost supernatural experience to me.

I'm not saying I would never have got round to Philip K Dick without seeing Blade Runner but it brought me there sooner. I own about a dozen and I've read a dozen more the majority of which were never made into novels and probably never will. I see that as a good thing. The reason that the source material isn't as good as the film is that the film has developed the material in the book. Dick was notorious for churning out material at breakneck speed. One can only imagine if, after seeing the film, he had written a novelisation of it. I wonder if that's ever been done. Answers on a postcard, please to …

So, what am I saying? The bottom line is that I think there are too many people out there who want to make issues about things. So Dick liked what they did with his book and Kesey didn't. The books are still there and if you didn't want your book turned into a multi-million pound extravaganza don't sign away the ruddy film rights.

Right now the latest adaptation is The Golden Compass and the reviews have not been that kind. Writer-director Chris Weitz has been swamped by the task of condensing a densely imaginative 430-page book. Something had to be left out and some would argue – not unconvincingly – that he chose to leave out meaning in favour of action. But it is what it is. The kids will be entertained. And if their parents have any sense they'll buy them the book for Xmas in favour of the plush 18" electronic talking bear.