I'm not sure how to write this without massive spoilers, so I'm just going to go ahead and assume that no one who hasn't read the full trilogy is likely to read this anyway. And if you haven't read the series, I highly recommend it!
Katniss, Gale and their families are now living in District 13, along with Haymitch, Finnick, Beetee, and the remaining refugees from District 12. Unfortunately, the rebels weren't able to rescue Peeta from the Quarter Quell arena, and he's being held in the Capitol at the mercy of President Snow. District 13 President Coin and the rebel leaders want Katniss to act as the Mockingjay, the public face of the rebellion as they fight, first for the districts and then to topple the Capitol government. She agrees, but has an increasingly difficult time as the war escalates and she knows the torture Peeta must be facing. When they realize that he is essential to Katniss' success as the Mockingjay, the rebels rescue Peeta along with several other prisoners of the Capitol. But his mind and memories have been altered with tracker jacker venom to view Katniss as his enemy, and it looks as though it could be permanent.
Mockingjay is the darkest and most disturbing of the Hunger Games trilogy, though none of the books are exactly fluffy. I knew that there would be casualties and deaths in the war, but I honestly wasn't expecting quite so many. I was particularly crushed about Finnick's death, and then absolutely blind-sided by Prim's. I never saw that coming. But it certainly was effective, if also heartbreaking, in confirming Katniss' suspicions about President Coin. During her conversation with Snow just before the execution, I finally recognized the significance of Coin's name, as in "another side of the same..." Katniss' retribution was poetic and excellent.
Throughout the series, I was inclined toward Katniss/Gale, though I liked Peeta and could definitely see the appeal. What I think I liked about Gale was their similarity, that he understood the way her (pre-Hunger Games) life had been in a way that Peeta couldn't. But the Katniss/Peeta ending worked for me after all. Of course, she would never have been able to separate Gale from Prim's death, but it's also true that Katniss and Gale may have been too similar for things to ever have worked out in the end. Katniss and Peeta complement and balance each other. And as sad as it was to read about brainwashed Peeta, I think his struggle to reconcile his memories with the truth also helped him to grow past his childhood infatuation with Katniss and see her in a more realistic light. And that must have made for a better and more honest relationship.
I'm sure there are deep thoughts to be had on the nature of power, but I'm not going to write about that. I'm going to write about what struck me one night when I'd stayed up far too late reading the first half of Mockingjay, and made me put down the book to scrawl this on a scrap of paper before I forgot.
What I love about Katniss as a heroine and about the series overall is that almost none of her success was hers alone. She was always willing and able to do whatever it took to survive, and she worked hard to develop the skills to make it happen. But she also knew when to accept help, even from that moment at age 11 when Peeta threw her the loaves of bread. She could never have survived either round of the Games or the later war if she hadn't been willing to give and receive help, even when she didn't entirely (or at all) trust those allies. I don't generally look for morals or lessons from books, but I'd say at least one of those from the Hunger Games was that no one can be a hero on their own, and I like that. I've been using this icon of Buffy for my Hunger Games posts because of the crossbow, but BtVS had a very similar theme, so I find the icon apt (APT!) for that reason as well.
So yeah, I'm super happy to have read the Hunger Games trilogy, and many thanks to everyone who recommended it!