Xerography had practically no foundation in previous scientific work. Chet [Carlson] put together a rather odd lot of phenomena, each of which was relatively obscure in itself and none of which had previously been related in anyone’s thinking . The result was the biggest thing in imaging since the coming of photography itself. Furthermore, he did it entirely without the help of a favorable scientific climate. As you know, there are dozens of instances of simultaneous discovery down through scientific history, but no one came anywhere near being simultaneous with Chet. John Brooks, Business Adventures: Twelve Classic Tales from the World of Wall Street, 2014 Ed., p. 191.
Typically, an invention happens when a number of people have a similar idea at about the same time, leading to extensive controversy about who really invented what. For example, the invention of the telephone led to multiple lawsuits, and the real inventor became a matter of legal interpretation determined by which side had the better lawyers.
Xerography, on the other hand, was an isolated invention. No one, other than Chester Carlson saw the possibility of combining a photoconducting drum, charged pigment particles, and thermal heating into a useful invention. Yet, these processes made the photocopier and the resulting billion dollar industry a reality.
makes copies of anything…on ordinary paper…even pages in a book!
Note added March 16, 2015:
In further support of the notion that inventions typically occur nearly simultaneously in multiple places, Kevin Ashton provided the following analysis in How to Fly a Horse (2015, p.51):
Because everything arises from steps, not leaps, most things are invented in several places simultaneously when different people walk the same path, each unaware of the others. For example, four different people discovered sunspots independently in 1611; five people invented the steamboat between 1802 and 1807; six people conceived of the electric railroad between 1835 and 1850; and two people invented the silicon chip in 1957. When political scientists William Ogburn and Dorothy Thomas studied this phenomenon, they found 148 cases of big ideas corning to many people at the same time and concluded that their list would grow longer with more research.
All About Images Blog 
As a secretary in the ’60’s I did a happy dance when my company bought a copier. So happy to throw away the carbon paper!
3d copies too 🙂