In the first chapter we establish how this civilization functions. The boys shot down over the
tropical island where the novel takes place, so you may visualize this island, whatever you feel like picturing there, it doesn't just have to be the thing written. I would for example imagine the smell of the sea. The boys are between civilization and savagery here and that is the main conflict in the novel.
The central theme of Number the Stars is the difficulty of growing up. One could make the case that Lowry uses the context of World War II as a way of making these difficulties stand out clearly.
