The premise of this book is that the natives of Gethen are neuter most of the time and only develop sexually during monthly cycles, during which they can become either gender. A mother of three can also be the father of two. There's no marriage, and sex during cycles depends on finding someone else in a cycle of the opposite sex. Le Guin was trying to make me come to grips with this, but I didn't have to because it was a fiction book. So I didn't bother. Apart from that weirdness, the book was pretty good. The prison escape and trek across the ice were exciting. Don't try it unless you're in the mood for bizarre.