Based on what I have read so far I believe the character that will experience the greatest change by the end of the book is Bruno. So far Bruno's life has changed dramatically from moving away from his beautiful, big house in Berlin to a dull, concrete house in the middle of nowhere surrounded by a dark forest with no one to play or interact with. Bruno describes his house back in Berlin, a happy, cheerful family home, with neighbourly children to play with, shops surrounding and busy streets to navigate through. As against this sad, unfriendly, lonely house where there are no neighbours, there are no shops, there are no cars and only a distant view of a barbed wire fence. By the time the story is over I believe Bruno will be well on his way to developing from a quiet boy to a questioning teenager. He will probably have a better relationship with his sister and ask further questions of his Mum and Dad as to what his Dad does for a career and why they moved so suddenly.