As other reviewers have said, this book is about what could happen in the future with regard climate change. It presents some ways that this challenge might be tackled. There is no story line as such. The chapters are more like a series of tableaus.
However, my big complaint about this book is the exceedingly high number of dreadful swear words that it contains. In its 563 pages there are 101 swear words which is roughly one every five pages. They are simply not necessary. It makes me wonder what dirt and filth fills Kim Stanley Robinson's mind.