The reading at the end ties into the theme of growth. Scout has grown throughout the novel, and this moment of Atticus reading to her is like a culmination of that growth. It shows that even as she has changed, their relationship endures and continues to shape her. It also reflects on the theme of education. Atticus has always been an educator, and this is another instance of him passing on something important, whether it's knowledge or values, to Scout.
It contributes to the theme of family. The act of reading shows the closeness between Atticus and Scout, highlighting the importance of family bonds.
At the end of the novel, when Atticus reads to Scout, it significantly contributes to the overall theme. One of the main themes is the power of love and care within a family. This act is a clear display of Atticus's love for Scout. It also speaks to the theme of morality. Atticus has always been a moral compass in the story, and by reading to Scout, he might be subtly instilling moral lessons. Moreover, it relates to the theme of the passage of time. As the story nears its end, this reading moment is a snapshot of where their relationship stands in the face of all that has happened over time.