Henry Darger was born in Chicago on April 1892. His mother died when he was four, and he lived with his father, a tailor, for another four years, until his father was put in a home. Henry initially lived in a Catholic boy’s home, and later was placed in the Illinois Asylum for Feeble-Minded Children in Lincoln, Illinois. He escaped from there in 1909, returned to Chicago, and found work, as he did for most of his life until his retirement in 1963. Between 1931 and 1his death in 1973 he lived a reclusive life in a second-floor room in the Lincoln Park area of Chicago, and there he wrote and illustrated the three massive works for which he is famous: one science-fiction novel, one fantasy novel, and a fantastical autobiography. The manuscripts were found in his room after his death.
What is now generally known as In the Realms of the Unreal, was entitled by him “The Story of the Vivian Girls, in What is Known as the Realms of the Unreal, of the Glandeco-Angelinnian War Storm, Caused by the Child Slave Rebellion”. There are some 300 water-colour paintings designed to illustrate this text. The story is of the seven Vivian girls who rescue other girls who have been captured and tortured during a very violent war. There are elements of Baum’s Oz books there, and much else, including the American Civil war and both World Wars. Darger himself was called up in 1917, but did not actually take part in action: there is almost nothing to report on his War Experiences. The book is 15145 densely typed pages long. Discussion of it has tended to focus on the psychopathology it reveals (the fact that the little girls are often depicted naked in the pictures, and with male genitals, has inevitably fascinated scholars) rather than on any literary quality.
If this is “science-fiction”, then the other fictional work is “fantasy” Crazy House: Further Adventures in Chicago (about 10000 handwritten pages) takes the seven Vivian sisters from their imaginary planet to Chicago, where they encounter a house possessed by demons and evil ghosts. The eight volumes of The History of My Life contain around 200 pages about his real childhood, and then 4672 pages of another fantasy about a tornado called Sweetie Pie.
Most of the above is taken from Wikipedia, supplemented (and corrected) by Klaus Biesenbach, ed., Henry Darger (Munich etc: Prestel, 2009). My thanks to John Clute (and the Encyclopedia), for alerting me to Darger’s military service.