Stanley G. Weinbaum 
The New Adam 

Edmund Hall, born a mutant with too many joints in his fingers and a double mind, tries to find a purpose in a society of humans. This superman is no caped crusader fighting for justice though. Rather, he is a dual-brained super-intellect with an IQ so far off the charts that normal human beings appear as Neanderthals next to him. In this story, our evolved human is born into modern society without anyone knowing his nature. While pondering whether he’s a superman or the devil, he explores pleasure, power, and passion. Slowly he realizes the differences between himself and contemporary humans, and therein lies a fascinating story.