This is probably one of the few blank spiral bound notebooks of good quality around. My quips with it are mainly stylistic personal preference (for example, I wish the outer corners were not rounded). The paper is indeed incredibly smooth to write on. It is not suitable for fountain pens though. Quite a lot of feathering and bleeding through.
Renown for its paper products, Japan's Kyokuto has been innovating the notebook product space since its founding in 1922.