I am compelled to contribute (belatedly!) what I know about Once Were Warriors: it is the first novel of Alan Duff, which was subsequently made into a movie.

Movie better than book: Enchanted April. Unfortunately I can't even remember the author (shocking! I hate when I forget an author's name) but the movie was brilliant. I read the book afterwards and thought it fine - until towards the end, when I realised the movie had made a substantial change in one of the relationships - and I liked the movie version MUCH, MUCH better. Made more sense and was so much more satisfying. It's still one of my fave movies and one I turn to when I'm distressed and need soothing and the rejuvenation of hope.