It definitely lulls around the first half of the second book, and maybe again at the beginning of the third. I still think it is great overall though, and the deep dives on ecology, the intricacies of the actual work required to create a new - utopian - society etc become quite vital to the plot as it plays out. Maybe I am just a massive ecology nerd but I enjoyed those parts, haha. I would say the payoff in the 2nd half of Green Mars is worth the drudgery though. Red Mars itself though is probably one of my favourite books ever written, so if nothing else I would highly recommend that.