Forum:SH:Opinion on reference books as The Art of The Clone Wars

What is the consensus about reference books such as "making of" and art books pertaining to the production of The Clone Wars series in this case. Since they talk about the development of a media and does not contain any story information, are they considered a canon or legends source, or neither?--Tetsu Aero (talk) 12:58, April 23, 2016 (UTC)