The Tunnel Under The World - Frederik Pohl

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? The protagonist, Guy Burckhardt, wakes up screaming from a horrible dream of explosions, searing fire, choking gas and other terrible ways to die. But he wakes up so it must have been just a bad nightmare, right? To find out that piece of information you will need to listen to this inventive and scary story. (summary by Phil Chenevert)