The Cleft by Doris Lessing (260 pgs) 2007
A stunningly good book, but difficult to categorize. It could be called a parable of the origins and evolution of gender identity.
In the beginning, there were women who spontaneously self-impregnated and only gave birth to women. Their idyllic (in both senses of the word) existence consisted mostly of obtaining food and enjoying the sun and the waves. Every day was like the next, and every woman as well. Because nothing ever changed on the large scale there was no strife, no strong emotion. Everything was the way it was, the way it had always been.
And then a male child was born.