DIRECTOR Stephen Frears was sceptical when asked to helm the screen version of Nick Hornby's bestselling novel High Fidelity. His worry was the prospect of transferring the story of a list-making, music-obsessed man with relationship problems from London to America.

"Then I read the script and thought it was of no importance where it was set. To my surprise I was convinced by what I read. I thought, 'this is a very good idea to set it in Chicago'," he recalls.

He talked to Hornby about the planned switch and found the author had no objection, pointing out his story was about people not places. Perhaps he was aware that the film would find a wider audience if it was set in the US and not England.

There has been much talk of late about film-makers taking liberties with historical facts in movies like U-571 and The Patriot. But the fate of High Fidelity demonstrates they're just as likely to rewrite books as rewrite history.

With High Fidelity, there was a happy ending. Both author and film-makers were pleased with the change of scene. At least the tone - and large chunks of dialogue from the novel - were retained.

That's not always the case.b Books and films are completely different forms of communication, and what works in print often seems ridiculous if transferred unaltered to the screen.

Best for authors not to visit the set to see what's been done to their book in the transfer from page to screen. Some are happy to hand over responsibility to someone else.

Amy Jenkins, who created cult TV series This Life, sold the rights of his first novel Honeymoon to US producers for a large sum. Robert Harling of Steel Magnolias and First Wives Club fame, has been chosen to write the adaptation. Jenkins is being kept informed of developments. "I'm absolutely fascinated to see what he does with it," she says.

As Thomas Harris rarely gives interviews we have no way of knowing how he feels about the controversy surrounding the filming of Hannibal, his sequel to The Silence Of The Lambs.

The project has been through development hell since producer Dino De Laurentis paid a record nine million dollars for the screen rights to the further exploits of Hannibal Lecter and FBI agent Clarice Starling. Various people have worked on the screenplay including Ted Tally (who adapted Lambs), playwright David Mamet and Steve Zallian, who adapted Schindler's List for the cinema.

One thing is sure - the ending has been changed in the version being filmed by North-East born director Ridley Scott. The book's finale to the tale of Hannibal the cannibal was rejected as too grisly for cinema audiences.

Just because a book is a bestseller doesn't guarantee that a film version will find favour with audiences and critics. The film of Tom Wolfe's acclaimed novel Bonfire Of The Vanities received damning reviews. Despite a cast led by Bruce Willis and Melanie Griffith, the picture proved an expensive flop.

The team of writer John Hodge, producer Andrew MacDonald and director Danny Boyle showed that a difficult book could be made into a commercial hit with Irvine Welsh's Trainspotting but tripped up when they attempted to do the same, with a bigger budget and US studio backing, for Alex Garland's The Beach.

Despite receiving other offers for the rights, Garland chose them because he liked what they'd done with Welsh's book. "They didn't seem too precious about their source material. They were basically film-makers and I thought they did a fantastic job with that," he says.

He even stood by them when they altered the ending of his book for the screen version.

Some authors have made a fortune from films. A succession of John Grisham legal novels, including The Firm and The Pelican Brief, were snapped up for the cinema often before they were even published.

Horror writer Stephen King must hold some sort of record for the number of books and stories that have been filmed.

The big question mark at the moment hangs over the cinema version of J K Rowling's Harry Potter novels. Steven Spielberg was among the film-makers mooted to helm the project but the task was eventually given to Home Alone director Chris Columbus, who made Mrs Doubtfire.

Whether Rowling turns out to be satisfied with the outcome remains to be seen when the movie, which begins filming this autumn, is released next year.