Most of the definitions of book that I have looked-up ~ in the various online dictionaries ~ mention that a book '...includes a cover'. I find this debateable ~ but that is a topic for elsewhere. Suffice to say that since everyone knows what a book is ~ and that books all have covers wrapped around them ~ why go on about semantics? If I am not going to define cover
then I'll compensate for that omission by illustrating some covers. (Which may include other parts of the book.)