What makes this book so good is how seriously Robinson takes political economy. While other authors might choose to skip past difficult questions about a full-scale international Mars colonization mission, Robinson takes some of the implicit questions very seriously: what would the composition of the crew be from a national/cultural perspective? What kind of implications would that have on the scientific nature of the work? How would being on Mars affect the crew psychologically and politically, and what would the long-term ramifications of those changes be with mission control on Earth?
All of these questions are more are thoroughly explored here, and I really liked the structure: each of the major sections takes a close third-person look behind one of the hundred original colonists; each of their personalities and characteristics shine through, and the book builds up to a thrilling climax that deals with both the issues considered around political economy and psychology.