For me, the most meaningful part of the story is the friendship between Max and Kevin. Each of them is alienated in his own way. Max feels like an outcast because of his association with his father and because of the way that he looks. He's huge. Max also feels that he's too stupid to be any good at anything. Kevin feels equally outcast, but for the opposite reasons. He's small, frail, and incredibly smart. Additionally, Kevin's health is declining to the point where it is life threatening. On the surface, these two boys have almost nothing in common and shouldn't get along, but they do get along. They get along great and have amazing imaginary adventures together. To me, the strength that Max gets from Kevin and vice versa is the most meaningful part of the story.