"Red Mars" in particular, and the remainder of the trilogy as a whole are quite simply the best novels I have ever read. Ever. And I have read quite a few, s/f or otherwise. I recommend this to everybody, whether they like science-fiction or not.
It starts out, as an epic soap-opera - for want of a better description - about a group of 100 carefully chosen scientists, sent on their way to establish the first permanent colony on another planet, and all their curious personal interactions. Halfway there, they decide - as one might expect to happen - if they are to start a completely new civilisation, why should they be controlled from another planet, and do everything in accordance with NASA protocol. There begins the rebellion, which - a couple of tens of thousands of new colonists later - develops into a guerilla war for the control and sovereignty of our second home.
Kim Stanley Robinson likes to set up interesting little philosophical arguments between the main characters (as in "The Years of Rice & Salt", also an excellent book), and thus we see the continual disagreement between those who believe we have a duty as intelligent space-faring beings to spread life wherever there is none, and those who believe there is intrinsic value in a barren but untouched landscape, and that it should be left well alone.
All the characters are very well thought-out and developed (Sax being my favourite), and with a few notably exceptions, all of the technology the author proposes is very "near-future".
I have no idea what was going through the minds of the people who gave this book "1 Star". They should probably tackle something less challenging first, like one of Enid Blyton's epics. This book is unashamedly big and long, but it is so, because it covers an important and epic story.
Some day we will do this for real, assuming we haven't already killed ourselves off - which is a distinct possibility.
Read it, and take it for what it is: an incredibly well-constructed epic story about the human condition, transplanted to another planet. I find this book truly inspiring, and it is one of the only few I re-read at least once every two years.
The second book is about 85% as good as the first one, and strongly recommended also. The third one mainly really ties up loose ends, and is definitely worth a read if you liked the other two, but is certainly nowhere near as groundbreaking.
READ IT. READ IT. READ IT. (Then read the other two).