It's fully Japanese though (and Kanji heavy), so the linked article is still helpful as an English overview for those not (yet) proficient in Japanese.
In this specific case, I think it's interesting that the english blog doesn't bring much (it just describe the books can have illustrations etc., info which could be immediately gathered by looking at the book samples), and the actual content, the books themselves, are of most uses for people speaking the languages or able to deal with it a way or another.
