 When we say the term hard science fiction, this is what we're talking about. It starts with a premise of what if the world was a little bit different and how would we live in it? In this book, people are living in a universe where gravity is many millions of times stronger than it is in the real world. They can feel the pull of each other when they get close to each other. And the way in which these people survive and the way they explore their world is so striking and so creative, I couldn't put it down.