In the final volume, Collins' rage against the Western Machine gives way to rage against human nature as Katniss goes to war. It's easily the best of the three books and brings everything to a satisfactory close - which is not to say that the ending is a giant ball of fluff. Indeed, Katniss goes through a few additional types of hell before all is done and gets a realistic, qualified, happily-ever-after.
There are still irritating flaws, even excluding carry-overs from the previous books but fewer of them. It's a shame that Collins did not take more time and care to ensure everything made logical sense in her world and to do some research on bows and hunting etc. as then this series would have been a towering achievement. As it is, it is the passionate anger driving the writing that makes these books worthwhile and everything wrong with them ultimately forgivable. Few novels are as compelling and few convey such ferocious anger. The Hunger Games trilogy tackles such a wide range of issues both contemporary and timeless in such a gripping and powerful way that I think it will still be read a long time from now, which is what any serious writer wants for his/her books, surely?