War
Clearly, the central theme of this novel is war, and what it makes one do. This theme explores the idea of needlessness of war. It explores the depravity and futility of it. The setting of the novel is war torn. There is only pain and suffering and rape and destruction. It is such a setting in which the industry of child soldiers thrives.
Innocence
Another very important theme in this novel is innocence. Perhaps by making the protagonist a child, the author wants to delineate just how vile and inhumane war really is. The story pivots around a child who ultimately loses his innocence and never really has a childhood. Hence, he is deprived of that innocence that every child must have.
Redemption
While one can say that because the protagonist was a hostage to misfortune and so not responsible for his actions, he does truly feel the need to redeem for his sins. He says that the Bible holds no meaning for him anymore, but the idea of redemption is universal. He understands that as a soldier, he committed a lot of sins, and wishes to be a doctor and save lives as an act of redemption.