The way this trilogy concluded was so satisfying (much more so than Mockingjay was to me). I love Todd and Viola and their connection to each other, the Mayor was fascinating, and so many other characters were fleshed out and more real. And even though the book is long, it's pretty intense and fast-paced throughout. While hearing the voice of The Return and The Sky was important to the story, I didn't enjoy those passages as much, and found it was hard to wrap my brain around the concept of their communication. I just suggested this series to someone again today, and will continue to do so now that I know how it all ends. 
 (I couldn't help picturing the aliens from District 9 as the Spackle.)