The movie makers did a much better job this time around. Not only did they stay truer to the book, but the major themes of the book remained in tack. They even added some of the humor (even though they still cut my favorite Peeta joke "They saw her shoot. Actually, I saw her shoot, for real, for the first time. I'm about to put in a formal request myself")
Even though they had to change a few things with Peeta, they did a much better job with him as well. In the first movie, I felt they made him too wimpy (having him cry on the way to the train, pa-leese). This time they showed off the charismatic side to the character and gave him the boldness he demonstrated in the books. All while still being him.
So let's take a look at the nigger differences from book to movie:
1) No Twill and Bonnie. The refugees from District 8 never appear and tell Katniss that District 13 is still around. This then doesn't spark Katniss to pay attention to the new cast and realize that the footage of District 13 is a fake.
2) Darius doesn't exist. This is the peacekeeper that defends Gale. He's later turned into an Avox and assigned to Katniss' and Peeta, most likely as a way of getting under Katniss' skin and shaking her up.
3) Plutarch Heavensbee never shows Katniss a watch. In the book, the watch is his way of showing he's on her side. It has a mockingjay hologram. It also signifies the design of the arena, to give Katniss a heads up as a new mentor. In fact, the movie set Plutarch up as having manipulated the Quarter Quell with president snow, slightly suggesting that they bring the victors in a tributes in a ploy to kill Katniss and "her kind". There's even a deleted scene of him switching the Quarter Quell envelope. This is not in the book as Plutarch specifically says he didn't know Katniss would be back in the arena.
4) Peeta, Katniss and Haymitch training as Careers. When it was decided that the victors were being brought back into the games, these three begin training and studying up in the other victors so they can be prepared and possibly win the games again. It's due to this that Peeta and Katniss watch the Quarter Quell in which Haymitch won. Katniss sees that he also defied the capital by using their own force field against them to kill a fellow tribute and ultimately win the game.
Even with this changes, nothing is taken away from the movie. This is how I like my adaptations.