Hard cover is a type of book binding that is used to protect the pages and content of a book. It is made up of two components: a SHELL and a CRUST. The SHELL is a hard, rigid material such as cardboard or plastic that is used to protect the pages of the book from damage. The CRUST is a thin layer of material such as cloth or leather that is used to give the book a finished look. Together, the SHELL and CRUST form a hard cover that can protect the book from wear and tear.