Just found this thread...
I and my wife got the opportunity to translate War Horse, the novel, into Swedish the year before the film opened. It was a little strange seeing the movie after getting really involved in the text, not because of the changes in the storyline, but because of the rather drastic change in point of view. In the book the story is told with Joey as the narrator, describing the events from his perspective, deepening the relationships with the other horses and a number of the humans, while the movie is told more from Albert's viewpoint with a completely "non-talking" horse. Both stand on their own, I think, but they also tell quite different stories. I haven't had the opportunity of watching the stage play, but I'd like to know if the play is closer to the book or the movie - or rather - is the play an intermediary between the book and the movie?
Things I like with both versions is that they show what a complete terror WWI was, and that the soldiers were both good or bad according to their personalities and the situation, and not because of a particularly evil ideology. The Germans were in it just as badly as the Allies.