One of my favorite topics in science fiction is super men. This must have been caused at one point with my father reading me the Odyssey. Odysseuss according to Homer was the greatest liar in the world. He was also a superhuman figure in many ways. I think my fathers reading me the Odyssey is what got me interested ultimately in science fiction and fantasy.
One of the first characters that is superhuman is Tarzan of the Apes by Edgar Rice Burroughs written in 1914. He is the primal englishman capable of overcoming the deep jungle. Although it is very entertaining reading, it is one of those books with an incredibly strong undercurrent of racism in it. Tarzan is physically capable, but not super smart. I enjoyed reading this book because it successfully transported me to a world like no other, the deep jungle.
The next book which focuses on a superhuman character is Gladiator by Philip Wylie written in 1931. This is truly fantastic story. It tells the story of a man injecting his wife with a super serum so their baby is super strong, super fast, and impervious to damage. It is a tragedy in every sense of the word. The boy when he grows up accidentally kills a man on the the football field gives up college and wanders the world. He does various daring things, rescuing ships, stopping robbers, and saving people all anonymously. In the end, unhappy, he asks god "Why me?" and is struck down by lightning. Gladiator is acknowledged as the book which created the idea for superman, the comic book character. It is a really excellent and tragic story.
As the genre develops in science fiction, the focus begins to change from superhuman physical powers to extreme mental powers. While Slan by A.E. Van Vogt acknowledges physical superiority for his mutant human "Slan" named Jommy Cross, his real powers lie in his telepathic abilities, and super keen scientific mind. It is here that the persecuted Slan differentiates himself from other humans. Slan is a classic of science fiction.
Following Slan in 1953 is one of my favorite science fiction stories, More Than Human by Theodore Sturgeon. This is a novel about six freaks who don't fit in with other people who have psychic powers. It tells how the group forms into a gestalt or group mind which transcends normal humanity and becomes more connected with a kind of universal mind. At this point, they are supermen because of their superior mental powers. Theodore Sturgeon writes a kind of strange science fiction focused on oddness and love. Two of his other stories which are quite interesting are Venus Plus X and The Dreaming Jewels.
Another classic novel about a superman, this time a man out of place, is the story of Valentine Michael Smith, a man raised by martians. This is the classic novel Stranger In A Strange Land by Robert Heinlein written in 1961. Valentine Michael Smith is a messiah figure who teaches people how to "grok" or become deeply in tune with things. He also seems to preach free love, mysticism, and meditation. This book was almost a bible of the counterculture movement in the 1960s.
You could call it the spiritual predecessor of the novel Dune by Frank Herbert written in 1965. The central character in the book, Paul Atreides is first trained as a mentat, a kind of human computer and powerful mind. He partakes of spice which both extends his life and expands his ability to predict the future. He is at both times a messiah and a superhuman mind. There are strong religious and ecological themes throughout this book. I have read this book many times. I can almost quote the book, "fear is the mind killer." I insist that you read the first book in the series. Don't watch the movie, though. I thought the movie was awful.
Now, I am skipping ahead for quite a while. Octavia Butler wrote a book called Parable of the Sower in 1994. The main character is a hyperempath, she feels what other people feel. This is both a curse and a blessing. When she loses her parents in a dystopian future she moves to the mountains where she establishes a religious community called earthseed. The second book, Parable of the Talents tells the trials and tribulations of her now found religion. Octavia Butler died before she could finish writing the third book. She claimed writers block for the third novel in the series. The religion which the hyperempath is founding is called "Earthseed", the ultimate goal being to colonize the stars. The difference with this type of superman is that the superman is crippled by their own abilities.
This is not a new theme, Olaf Stapledon wrote a book earlier called Odd John about a person with superhuman intelligence who ultimately gives up his own life by disappearing into a fiery chamber. There is always a niggling feeling that Odd John never died at the end, but we can never confirm it.
All of these books are really good science fiction well worth reading.