I really enjoyed the first two of Sagan's books in this series (Idlewild and Edenborn) but the conclusion is even better.
The series is about (spoilers for Idlewild follow) a world in which a terrible plague killed all humans. The first book begins as the protagonists find this out - they're a group of engineered posthumans who were created to find a cure to the disease and cure those 'survivors' who got into cryonic suspension before they died.
This book has the posthumans beginning to waken and cure these people, and deals with the problems of getting society working again with only a few thousand people (almost all from the extremely rich or politically powerful classes).
It's a fairly cynical book, but there are victories as well as defeats. Sagan also does a good job of exploring his posthumans' reactions to the situations. He also differs from almost every other similar story I have read in not pushing any overt political message here. It seems to be more of a pessimistic humanism pervading the story - definitely a particular philosophy, but not a suggestion that one political arrangement will sort everything out (especially as it seems like the suggested system is usually some kind of libertarian arrangement).
It also seems like it would read well as a stand-alone novel - I certainly had forgotten most of the details of the first two books, and that didn't really matter. The previous novels inform the motivations and relationships between the posthumans, but as this story is about their relationships with the survivors, that's not really so important.
Overall, great novel.