Do you need any prizes for guessing who it is ! :)
Men are from Mars, Women are from Venus - the most famous relationships book ever published written by John Gray.
The first chapter starts like this:
Imagine that men are from Mars and women are from Venus.
And the couple of next paragraphs talk about how they fell in love and ends saying that for years they lived together in love and harmony.
And the story goes as follows, quoting from the book:
Then they decided to fly to Earth. In the beginning, everything was wonderful and beautiful. But the effects of Earth's atmosphere took hold, and one morning everyone woke up with a peculiar kind of amnesia-selective amnesia!
Both the Martians and Venusians forgot that they were from different planets and were supposed to be different. In one morning, everything they had learned about their differences were erased from their memory. And since that day men and women have been in conflict.