This is a fine title for a book that's both a sequel and a middle book in a trilogy. The Hunger Games sets everything up, and Mockingjay brings it all together. So, as the second book in the trilogy, Catching Fire has to link the beginning and end, keep readers' interest, and further the story while also getting us fired up to read the third installment. You know, like Tolkien's The Two Towers: not the exciting beginning stuff, and not the gripping conclusion to an epic saga. That describes Catching Fire perfectly.
The Hunger Games helped prepare the people of Panem for the possibility of change, and Catching Fire is about igniting that change (pun intended). The people of Panem are like a pile of nicely stacked kindling waiting to be lit. They just need a "spark" to incite them into flames. As President Snow says, Katniss could be that spark:
"Katniss Everdeen, the girl who was on fire, you have provided a spark that, left unattended, may grow to an inferno that destroys Panem," he says. (2.31)
The first section of Catching Fire is even called "The Spark," as if to reinforce our understanding that the purpose of the book is to watch as Katniss, almost in spite of herself, "sparks" the "inferno" that will lead to a revolution and inspire the events of Mockingjay.