The story begins with a writer sitting at typewriter, he senses something behind him, he turns to see a shimmering disc floating in the air. Suddenly a man falls out of the disc, and it is a duplicate of himself... a second duplicate jumps out of the disc and a scuffle ensues. The writer is pushed into the disc and falls through it into a corridor. As the story unfolds, the writer becomes each of the duplicates in his efforts to return to his own dimension.
I read the story in a book of short sci-fi stories around 1972/73 and I'd love to read it again. Does anyone know what this is?