Arguably, around 80% of notebooks are plain black. That's not neccessary.
In the quest for the blackest black, “Vantablack” is currently the ultimate champion.
Currently in ZEITMagazin: The Cloud Book by nuuna by brandbook
Bonjour Paris! nuuna at Maison&Objet 2016
Paper art of Gunjan Aylawadi
Takeo In Tokio - A Puristic Paper Paradise
Innovation at hot-foil embossing