An article I recently read listed Stephen King as the first popular author to publish an e-book. A bit of searching revealed that they were probably talking about
Riding the Bullet, a ghost story published electronically in 2000 by Simon and Schuster.
Not only did this seem pretty recent, but I also had in the back of my head a rumor (that I definitely heard before 2000) of a William Gibson book, distributed on diskette, and in a format which erased/encrypted itself as you read it. Did the author of the article not consider William Gibson a popular author? Or is a book sold on diskette in program form enough of a "hard copy" to not be considered an e-book?
No, it's much stranger than that. It sounds like the book in question is
Agrippa (a book of the dead), an art book from 1992 printed with "fading ink", which included (in a hollowed out cavity) a diskette containing a
poem by William Gibson. There is a lot of conflicting information about this book (including outright denials of its existence by the author, artist and publisher) but the above-linked UCSB site appears to be the authoritative source on it.
I can't explain why, but I think I might have nightmares after viewing the "transmission".