Terraqueocosm by Anthony Ayoub
Approx. 87,930 words.
Published on January 22, 2010.
In desperation, a young couple who happen to be scientists, successfuly manage to transfer the dying man into the body of a mentally damaged young woman.
He successfully joins with the woman's subconscious and is able to access the full potential of their joined intellect.
Their new enhanced potential allows them to launch an effort to raise humanity to a new level.