As I did before in movie suggestions, I am once again overstepping my limit and humbly suggest you a wonderful sci-fi book which I am reading right now. Surely, you can say " Who the hell do you think you are? A book critic! I don't have time for this!" or " You haven't even finished reading the book, how dare you comment on it! And I would reply as " Hey dude, calm down. Yes, I haven't finished the book but this one is so wonderful already, I think that I should tell something about it. If you don't want to read then ......."
Anyways, by not spoiling the book: The story passes though in a planet which is named as " winter " As you can understand it is very cold planet which shaped the physiology of the homo sapiens inhabitants through evolutionary process. However the point that makes this book extreemly impressive is that these inhabitants are androgenic and only in specific times of the year they transform to male or female in accordance with their hormonal status. So, one could be male and female in the same year. It is such that a mother with a few children can become a father of another child! Surely it is observed in nature as in snails,slugs worms, sea cucumbers/sea stars/sea urchins etc. and some fish. However ff you ask me as a molecular biologist, I would tell that it is very unlikely this transformation in such advance creature like us.
Anyways, regarding this biological phenomenon,it is a world that the sexual identity is not used for the social status and as a tool of power. One of my favourite writer, Ursula Le Guin creates very interesting psychosocial model to describe this universe as she did in her novel called as " The Dispossed ". The difference between "friendship" and "love" is meaningless; (So farewell the consept of friendzone!) the tendency of dualism to determine human thought diminished; the basis of the duality of humanity as strong / weak, protective / guarded, dominant / dominated, possessive / possessed has declined.
So long story short (damn, I finally used that phrase!), I intensely suggest this book, you will not regret it.