Don't know if this rings a bell with anyone. Simulcrum? was probably the first book I've ever read about a virtual world: Protagonist almost dies when a road is chopped off in the middle of nowhere over a black void. Turns out that earth as we know is really a simulcrum/artificial/virtual world created by 'others' to test advertising. Occasionally there is a glitch like the road up above. People are reprogrammed to forget the incident. Protagonist experiences a reverse feedback where his virtual mind takes over the mind of the 'other' operator. I may be way off on the title and author. Publication date somewhere in the early 60's. Pretty sure it was an english translation of a French SF book.. thanks! Phlip