I would almost say that the underlying theme in this novel is struggle and change. Jason, through the space of a few months (summer and now into the school year) faces some challenge in each of the chapters and we cheer him on as he overcomes and grows. But there are several threads of struggle that wind through each chapter from the very beginning.
One is, of course, his personal struggle to master his speech and eliminate or at least sidestop the stutter that affects his confidence and his interactions with others. The other is the situation with the relationship between his father and mother. The story opens with a mysterious phone call wherein the caller hangs up without speaking. We suspect a mistress. What Mitchell shows us are no direct confrontations. He shows us the mother speaking with her sister about some suspicions. He shows us the mother and father arguing about money being spent. We see Jason accompany his father on a business trip and get a clearer picture of the man and his shortcomings as well as his fears. We see Jason with his mother, now an entrepreneur, and how she has managed to cope with the situation in her marriage by becoming successful.
And through it all, we see Jason’s growing understanding of others as he himself is in a constant battle with bullies.