h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

...as good as the books they are based on?

Who was it that made the decision to cut parts out of the movie version of the first ever 'book-to-movie' project?

What were the reasons for the omissions?
Lack of funds? Lack of time? Lack of film?

What would movies be like today if this (for lack of a more suitable word) 'trend' hadn't cottoned on?

Actually as I understand it there is a very good reason why things are cut from the storyline when a novel is made into a movie. For everything that you put in a screenplay you need a page of script to cover it. Each page of script is equivalent to one minute of screen time. Take the 5th Harry Potter book (whose movie comes out soon). It's 870 pages long. Divide that by 60 (min) and you would end up with a 14 hr 30 min long movie if you kept to the idea of one page of book = one page of script. Not only would it be too expensive to film but it's likely not many people would sit for over half a day to see it.

Because the novel and the film are two distinctively different forms of storytelling. Each has its own rules and devices to engage their audience's attention.

For example, how would you film this excerpt from John Buchan's 'The 39 Steps'?
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"The only occupants of the carriage were an old shepherd and his dog–a wall-eyed brute that I mistrusted. The man was asleep, and on the cushions beside him was that morning’s SCOTSMAN. Eagerly I seized on it, for I fancied it would tell me something.

There were two columns about the Portland Place Murder, as it was called. My man Paddock had given the alarm and had the milkman arrested. Poor devil, it looked as if the latter had earned his sovereign hardly; but for me he had been cheap at the price, for he seemed to have occupied the police for the better part of the day. In the latest news I found a further instalment of the story. The milkman had been released, I read, and the true criminal, about whose identity the police were reticent, was believed to have got away from London by one of the northern lines. There was a short note about me as the owner of the flat. I guessed the police had stuck that in, as a clumsy contrivance to persuade me that I was unsuspected."
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(taken from http://www.authorama.com/thirty-nine-steps-4.html)
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You could say we should use a voice-over to narrate this. It's widely known that a typical cinema audience can only tolerate small amounts of a voice-over narration. So, many experienced scriptwriters tend to trim it down to two filmable action lines with a couple of dialogue lines as a summary of that excerpt, or just simply cut it out altogether.

When a scriptwriter adapts a novel, it's a constant stream of dilemmas and compromises, but it's always understood that every scriptwriter's main aim is to convey the story's central message as well as to put out an interpretation of this message.

In other words, we shouldn't view a film adaptation as the visual form of a novel. We should view it as a film-based interpretation of a novel.