19 books in series

Buffy the Vampire Slayer Classic

Buffy the Vampire Slayer Classic is a 19-book series with 19 released primary works first released in 1999 with contributions by Andi Watson, Jen Van Meter, Doug Petrie, Christopher Golden, James Marsters, Jamie S. Rich, Chynna Clugston Flores, Tom Fassbender, Jim Pascoe, Chris Boal, Fabian Nicieza, Scott Lobdell, Paul Lee, and Amber Benson.

Buffy the Vampire Slayer: The Remaining Sunlight
Buffy the Vampire Slayer: Uninvited Guests
Buffy the Vampire Slayer: Bad Blood
Buffy the Vampire Slayer: Crash Test Demons
Buffy the Vampire Slayer: Pale Reflections
Buffy the Vampire Slayer: The Blood of Carthage
Buffy the Vampire Slayer: Spike and Dru
Buffy the Vampire Slayer: Food Chain
Buffy the Vampire Slayer: Autumnal
Buffy the Vampire Slayer: Out of the Woodwork
Buffy the Vampire Slayer: False Memories
Buffy the Vampire Slayer: Ugly Little Monsters
Buffy the Vampire Slayer: The Death of Buffy
Buffy the Vampire Slayer: Note from the Underground
Buffy the Vampire Slayer: Viva Las Buffy!
Buffy the Vampire Slayer: Slayer, Interrupted
Buffy the Vampire Slayer: A Stake to the Heart
Buffy the Vampire Slayer: Oz
Buffy the Vampire Slayer: Willow & Tara