To solve a problem wherein since many conventional book covers are fully transparent or opaque, the fully transparent book covers allow their owners to easily confirm the book contents but make the owners care about others' eyes, and the fully opaque book covers can reassure their owners because the book contents are not visible but make it difficult for the owners to distinguish the book contents.

Portions corresponding to a cover, back cover and spine, respectively in a book cover are divided into three stages in accordance with transmission visibility which are transparent, translucent and opaque. In regard to at least transmission visibility, among the three portions, a difference at one stage or more is made (for example, the portion corresponding to the spine is transparent and the portions corresponding to the cover and back cover are opaque.). Due to this division, the degree and speed of visual recognition with respect to contents described in the binding of the book vary with its owner who knows which portion has excellent transmission visibility beforehand and others who do not know. This enables the owner to directly confirm the contents and makes it difficult for others to view the contents.