Is the author Carolyn Keene dead?

Carolyn Keene is not a real person. It's a pseudonym used by a number of different authors who wrote the Nancy Drew mystery series.

The first author credited as Carolyn Keene was Mildred Wirt Benson, and she wrote the bulk of the early Nancy Drew books. However, many other authors contributed to the series over the years, and the identity of the author often changed depending on the book.

Therefore, while individual authors who wrote under the Carolyn Keene name have died, "Carolyn Keene" herself does not exist and therefore cannot be dead.