This is a set of 8 picture books from Fureberukan. When left out, children would pick them up, and I think they naturally acquired various knowledge. When asked something, I could respond with, "Why don't you look it up in the picture book?" Only "Chikyu to Kankyo" has a cover; the others do not. These are used children's books, so there are signs of being opened, folds, and tears. Please refrain from purchasing if you are sensitive to such imperfections.