The ideas in here are incredible - it's clearly been given enormous amounts of thought and research, and parts of the book are absolutely fascinating. It feels slightly churlish to say that where it didn't work so much for me was the characters... especially as I think the biggest character in this is Mars itself, which was vivid and immense and really the the best part of the book for me, far overshadowing the humans. There were a lot of people characters that I got sick of very quickly... to be honest, I didn't care in the slightest about a single one of them. I found it hard to see them as anything but walking philosophies: this is the person who thinks it should be preserved as much as possible, this is the person who sees it as a resource for Earth to exploit, and so on. I wasn't sorry when they all began to die; the planet itself was far more interesting.

I don't know if I'm comparing it unfairly to Aldiss' White Mars, which I read years ago and which left an extraordinarily deep impression, but I managed to unearth a copy of the latter (it turned up in my mail box recently) so I'll have to read it again to see how they compare.