I was hoping for a little redemption in this book. Apparently Collins felt it necessary to unleash a holocaust--it certainly felt like it.
Having read much history, and many troubling books, I have to say that Mockingjay is one of the darkest books I've ever read. Is this really meant to be read by youths? Rather, it takes the form of a study in post-traumatic stress disorder.
Aside from the appalling, unrelenting violence and death (it makes the Hunger Games look like the Olympics by comparison), I found it difficult to accept the casual death, often in aside, of fairly major characters. Some of them deserved better.
Additionally, the playing out of the romance, built up over hundreds of pages, was mostly unsatisfying: One of the principal conflicts of the series (Gale vs Peeta), that was very close to the surface throughout recedes to the background via its resolution in the epilogue.
Those complaints aside, Mockingjay did an effective job completing the series: Most conflicts were resolved--one way or another. I would say it was certainly not predictable. Collins continues to shine in many passages. Now, where are my anti-depressants?