This book also does a better job with the scientific parts than Red Mars, despite being more "romantic and out there". It is very focused on the terraforming effort, and several important things are going on. I won't mention them, for the sake of those who haven't read it, but I guess I've already given away the fact that the Reds don't have much pull. Other topics of scientific research that Robinson delves into are botany, artificial intelligence, sociology (personal relationships, in particular), and neurobiology.
Also, as Kalie Ma mentions, there is growing political arenas, both on Earth and in the Mars underground. Again, the main argument is about terraforming, though of course the issues of tradition are thrown in as well as any number of others. Typical for politicking.
<timeframe>I think that during the book, the 100th anniversary (in Earth years) of landing on Mars occurs.</timeframe>