Why is this page only focused on book designs?

Because book designing is a genuine and independent branch that requieres a designer to be able to communicate with a specific kind of audience. It requieres expertize and experience in the publishing industry, and the designers familiarity of the tastes and expectations of the bodies in the industry (book sellers, book distributors, media and the reader). Book designing should be interpreted as a subdivision of the design realm and is a branch of visual design that has a long heritage, numerous traditions and a unique design language. Book designing is communcating with an audience through the visual aesthetics of a book and should therefore be accepted as a unique discipline.