You know the drill by now. Some people trapped in a dystopic nightmare got tired of sending their kids off to the annual deathmatch, and once Jennifer Lawrence came along and showed them that the Capitol could be defied through the power of teamwork, they all came together to act on this new knowledge / long-standing grievance.
Other than mentioning the second act’s surplus of death traps, anything at all I could discuss about the plot would be a spoiler, so I’ll just say that the second half of Mockingjay’s adaptation continued to deliver on the promise of the rest of the series: to remain as faithful as possible to the original story while jettisoning everything that held it to the level of teen melodrama rather than realizing its potential greatness. I don’t know that I’ve ever said, “Naah, just go watch the movie.”
 Because if you can’t have teens killing each other, you can at least still have the environment trying to kill a lot of folks to make up for it; this is still a Hunger Games movie, after all!