Everfree is a satisfying but underwhelming conclusion to Sagan's overall very enjoyable trilogy. For some reason, the novel lacked the clear and enticing vision of the first part, as well as the touching and at times heart-wrenching character sketches from the second.
Basically, it's a wrap-up, speculating on how humanity might slowly rebuild from cryostasis, after being practically decimated by an epidemic. Sagan's picture is cynical, but not overly so, tending toward what I would consider a healthy scepticism about human nature.
It's just too bad for the story that this preoccupation with the rebuilding of societies and the consequences of that seem to push the more emotionally satisfying interactions between the characters from Edenborn too much into the background. And honestly, for me, that was where Sagan's main strength as a writer lay.