Incredibly good book. The deep, long, and plausible plot propels the finely sculpted characters through their decades-long effort to settle Mars. I haven't enjoyed a book this much in years; probably since reading Neuromancer as a teenager.
This book is definitely going to be over the heads of some readers; there aren't many cheap thrills or forced cliffhanger moments. Instead, it satisfies on a deeper level, keeping the reader engaged in a long-term relationship with several different characters--some of them deeply unlovable--and in the ultimate fate of Mars as a world inhabited by people.
It's a very ambitious book, and it succeeds.