I recently saw this movie twice.
I have read the books, and yes it makes a difference.
I don't know what you'd think of Katniss if you haven't read the books, I suspect you'd think she's a bit thick.
This is a looooooong movie. I like long movies, plenty of time for character development, plot details, and hopefully great scenery.
Sadly I watched Catching Fire in THE most uncomfortable seats, in the MOST noisiest of cinemas ever. I was distracted by people starting to get up presumably to go to the loo. I was surprised, because it didn't seem all that long to me. I was engrossed in the detail of the plot. Having read the books at the beginning of the year I was being reminded of the plot's details as we went along. It seemed true to the book in the most part.
I found the acting ranged from satisfactory to excellent. One stand out for me was Maggs, played by Lynn Cohen, who has worked in a great body of works since the 80s but this time, she has no dialogue. She can only express herself with gestures, and facial expressions. Hollywood, being what it is, ensures the most challenged of us are covered by other actors filling in the blanks for us, in case we need it, but I found Cohen's acting left me in no doubt of what she was thinking and feeling. Truly very powerful.
Its easy to think that Katniss is a lot older than her years, and therefore she appears a tad dense, not naive and young, and just plain scared. In the book we are privy to her fears, her nightmares, her overwhelming sense of responsibility. Although an attempt is made to let us know she is fearful, I feel the sense of urgency and depth of fear is seriously lacking in the the movie, though I am at a loss of how they would portray it differently, without narration, or changing the plot in some manner.
The garish costumery and make up of the Capitol, remain interesting with gowns made of life like butterflies or dresses with hip lines that are reminiscent of the renaissance era (albeit with a much shorted hem line). Amazing shoes to be seen, and Katniss wedding dress transformation is something to be seen (nope not a spoiler - that's all I'm gonna say).
Filmed in Hawaii, the jungle scenes do actually look like one, most of the time.
This movie brought to life for me some of the things that I found lacking in the book, for example the arena seemed less clear when reading the description, however in the movie it made simple clear sense.
Its a must see, but if you don't like long movies, save your money, your comfort, the comfort of others around you and your kidneys and see it on the small screen. Let the fans enjoy themselves.