4 books in series

Avatar: The Last Airbender & The Legend of Korra artbooks

Avatar: The Last Airbender & The Legend of Korra artbooks is a 4-book series with 4 released primary works first released in 2010 with contributions by Michael Dante DiMartino and Bryan Konietzko.

Avatar The Last Airbender: The Art of the Animated Series
The Legend of Korra: The Art of the Animated Series--Book One: Air
The Legend of Korra: The Art of the Animated Series Book Two: Spirits
The Legend of Korra: The Art of the Animated Series--Book Four: Balance