What is the theme of the novel?

The book Catching Fire has couple of themes.

Loyalty. It is shown between Peeta and Katniss. They are helping each other to survive. They had to be loyal to one another. Otherwise they would start going vs. each other and both die.

Government Control. It is shown through the whole book. The Government of Panem controls everything, the way of life of all citizens, where to live, what to eat, where they are allowed to go. As a way of showing their control they invented the Hunger Games that are repeating every year. In the games teenagers fight to the death. It seems like the games control not only lives of tributes and their families but everyone’s lives.

Rebellion. Katniss gave a spark of hope to everyone when she put poisonous berries in her mouth during the Hunger Games at the end of first book. That spark showed citizens of all districts they should rebel versus the capitol.