I think that coming-of-age angle is probably the biggest gain from splitting this book. It wasn't something that really came across to me from the book - at least, not as a major theme, anyway. But by splitting up the story for the film, it has become the central theme of the first part, which is really good. I suspect it won't be anything like so prominent in the second part, as the action heats up and the big battle approaches. But it was nice to take time out and focus on it separately in part I.