Uncle Geoff,
I don't know that one - I'm going to have to try and hunt it down at the library to be able to reply to your suggestion.
My problem with translating books into film is that I often don't want to see my favourite novels turned into movies as I don't want my imagination to be tarnished for the next time I read them. So if I were to pick a book to move onto the big screen it would probably have to fall into the category of 'really enjoyed but won't read again'. Unfortunately that category is pretty small, but one set of books that I think fits right in there is the Otherland quadrilogy by Tad Hamilton. I thought it was great eventually, but wow that first book was a slog to get through. I also think it would make an interesting film, if they could work out how to incorporate the separate plots that don't really come together until the end of the first (huge) book. It is mostly set in virtual realities so there is huge scope for pretty visuals, but has enough character development that it wouldn't be all about the special effects - there is actually a plot there too.
I've really enjoyed the recent adaptations of Pratchett's Hogfather and Colour of Magic (haven't yet seen Going Postal) and I think they retain the essence of the book's humour but also manage to stand on their own. They don't trespass too much on my imaginings of the characters in the book and stand as seperate things in their own right. Having said that, the books they've chosen to interpret certainly aren't my favourites in the series so maybe I'll feel differently when they get round to doing lords and ladies! Lord of the rings was very well done too, but that is film-making on such an epic scale that it isn't possibel to give that kind of treatment to every cinema interpretation of a novel.
Probably the best film adaptation of a book that I can think of is The Princess Bride by William Goldmann - the book and the film match in tone perfectly, right down the footnotes/narrators voiceovers and I think both are wonderful fun!
Vinx