Tritonia

The Tunnel Under The World is a science fiction novella by Frederik Pohl first published in 1955.

This famous Pohl story explores cybernetic robots and implanted personalities in a way that certainly expanded my way of looking at reality. Is that wall really real? or is it just kinda, sorta real? And who am I? 

Our protagonist keeps waking up on the same day, albeit unknowingly, and has strange experiences but fails to recall them after falling asleep. This goes on until he chances to escape the "reset" and sets about trying to discover what's happening to him. An interesting "put yourself in their shoes" story.

This is actually a horror story and the end won´t fail to send a shiver down your spine... 

The novella has often been anthologised, notably appearing in The Golden Age of Science Fiction, edited by Kingsley Amis (1981). The Tunnel Under the World was first published in 1955 in Galaxy magazine. 

Frederik George Pohl, Jr. (1919-2013) was an American science fiction writer and editor, with a career spanning more than seventy-five years. From about 1959 until 1969, Pohl edited Galaxy and its sister magazine If; the latter won three successive annual Hugo Awards as the year's best professional magazine. He won four Hugo and three Nebula Awards.

The Science Fiction Writers of America named Pohl its 12th recipient of the Damon Knight Memorial Grand Master Award in 1993 and he was inducted by the Science Fiction and Fantasy Hall of Fame in 1998.