Beloved author L.J. Smith has passed away aged 66 following a battle with a rare autoimmune disease.

Smith was best known as the author of The Vampire Diaries, which sold millions of copies and became a hit TV show.

The author was also known as a prolific ghostwriter who would repossess her characters after being fired or replaced, reports the New York Times.

Smith died on March 8 in Walnut Creek, California, and her partner Julie Divola announced her death this week, saying she passed away after fighting an autoimmune disease for over a decade.

The author sold millions of books and published more than two dozen works over her career, and had reportedly completed three more unpublished tomes before she passed away.