KXLY.com posted an interview with Josh Hutcherson where he talks about staying true to the book. You can read the entire story Here.

"There are things that have to grow and change from a book into a movie to make it work, cinematically. For instance, in the book, Katniss has an internal monologue going on the entire time and expresses what's going on inside her mind; but in a movie, you can't have that much of the narrator. It was not at all the kind of movie we wanted to make," Hutcherson explained. "So artistically, we had to find a way to convey the emotions, thoughts and ideas through the scene, situation and dialogue without it being expositionist garbage."

Sources: Hggirlonfire.com