I finished Kim Stanley Robinson's 2312, and I really enjoyed most of it. Like most of my favorite sci-fi, it matches a pretty sweeping backdrop and heady ideas with a few solid, believable characters rooted in relatively straightforward problems. (IMO, Iain M. Banks is still the master of this big, colossal universe and issues vs. two or three well-written, relatable characters).
Robinson isn't afraid to hide his agenda -- the Earth as we know it is going to be destroyed by human rapacity, and even colonizing other planets, moons, and asteroids (mostly asteroids) isn't going to solve some basic problems.
The climax of the novel (SPOILERS!) is the "re-wilding," where the two main characters manage to stage a massive re-population of the Earth's wildlife and, by extension, a revitalization of our planet's ravaged ecosystem. The book really shines here, as Robinson matches a breathless narrative to some pretty complicated (for an idiot like me, at least) earth science / ecology issues.
Unlike Banks, Robinson doesn't seem to think interstellar travel will ever be a possibility for humans. And so the stakes become even higher for a fully revitalized planet. He suggests that the human species is so unconsciously tied to Earth that extended periods away from the planet will directly lower one's life-span. People who live off-Earth, "spacers," are common enough, but without the occasional trip back to our Mother Planet they basically stunt their own life-spans or go crazy.
This is the first Robinson novel I've read, and I'm curious to pick up The Mars Trilogy, of which I take it 2312 is something of an addendum. Still, I had no problems going into this one "cold" without having reading some of his earlier work.
Also, his take on the future of gender norms and sex is pretty mind-bending. There are some moments of actual, literal poetry as well, which was welcome and unexpected in a "hard sci-fi" book.