Nintendo has announced that it will release a Splatoon art book in Japan. The art book is slotted for a release on October 10th, and will feature more than 300 pieces of artwork and other images centered on Splatoon. This art book will cost roughly 2,400 Yen, which comes out to about $20 USD.
Unfortunately, Nintendo only made this announcement on its Japanese website, and all mention of the art-book remains absent from their English media channels. Therefore, we do not know if this art-book will be released anywhere in the west.
We will keep you updated on any news concerning a release outside Japan.