I actually liked it a lot, though it did take me a while to get into the war bits, and I didn't enjoy them as much as the multiple narratives bit in the first half. And it probably could have been a bit shorter. But as someone else said, the multiple narratives bot wokred well, its didn't feel pretensious or experimental for the sake of being experimental. It was like a tense, engrossing game of Chinese whispers. The characters were all pretty intersting I though. And I like the way that it allowed the children characters to have some-what complex personalities, as children in literature are often far to one-dimensional in my opinion.
I'm not sure how I feel about the movie, aparently its going to star Keira Knightly who I haven't liked in anything since Bend It Like Beckham. I think it will loose all the bits that made it interesting and be reduced to a pretty basic war/love story. Blah.