L.J. Smith, the author of the Vampire Diaries novels as well as dozens of other young-adult fiction books, has died at the age of 66 after a years-long battle with a rare autoimmune disease.

The CW series The Vampire Diaries was incredibly popular when it debuted in 2009. It ran for eight seasons and spawned two spinoffs: The Originals and Legacies. It's easy to compare the three ...