Naruto Hiden (NARUTO -ナルト- 秘伝, Literally meaning: Naruto Secret Chronicles) is a light novel series which explores the stories of various characters after the conclusion of the original manga. Though each book is illustrated by Masashi Kishimoto, they are written by different authors. It’s also a part of the Naruto Project.
The Naruto Hiden series is followed by the Naruto Shinden series, which begin publication in fall of 2015.