One of my all-time favourites "The Dark Is Rising" was made into a film last year.
Didn't go to see it as they changed everything including the personality of the main character and the director was allowed to put a Christian moral slant onto a modern American background, when the story is set in rural England against a background of English folklore.
Biggest turn-off was casting Ian McShane (short and dark) as the "Merlin" character when the description given in the book and - therefore held in everyone's mind's eye - was of a tall, gaunt silver-haired man - much more like Christopher Lee. The book was magical, the film was, I'm told, very lame. I didn't even bother to go to see it as reviews from other lovers of the book put me off. Apparently it was only screened for a week in the UK.
I'm interested in the Secret of Moonacre, too, but don't think I need to borrow a kid as I've never really grown up!!
Hope they haven't spoilt it for you Jinnyj.
Saw The Kite Runner, last night. Pretty deep stuff. Very moving.