The book is set in a space-station, but it is not science fiction. In some ways it is more of a nature book, with extended detailed observations about seeing the earth from space. There is a bit of a plot, but that is more of a thread holding it together rather than driving the action. There is no action really, the characters are necessarily passive, observing the earth and thinking about it. The redeeming feature of the book, and I guess the reason that it won the Booker, is its beautiful prose. It is lyrically, almost poetically written. I read many sentences for a second time, which is not something I normally do, and I noticed that the text required more concentration than usual.
There is a debate with some people about how much authors can put themselves in the shoes of very different people (gender, ethnicity, etc). Harvey has never been into space, and yet I read that astronauts said that she had captured their experience perfectly. That is an amazing feat.