No no... it is not a joke. According to a news published at Tech-on, Fuji Xerox developed a prototype of a color electronic paper that can be written with an optical system.
Electronic paper is a rather recent invention, and some prototypes are already tested in some practical applications like (guess...) advertisements and bus stations time-tables.
More details about how the system works can be found here, and I wonder if this technology will become cheap enough to create e-books. Can you imagine to store thousands of books in your pocket (on an flash memory) and be able to read them anywhere?
