Form and Function are Closely connected in books. The physical appearance of books indicates purpose and intended readership. A combination of size, type, and page layout offers visible signals informing the reader of the content before he begins to read a book. Books that look different are different. They have different subject matters, purposes, and readerships.
Anyone browsing in a bookstore in the late twentieth century knows this. Today an illustration on the cover provides the most obvious clue concerning the subject matter and purpose of a book. When the cover shows a handsome man with a scowl on his face and a gun in his hand along with a beautiful young woman in distress—and possibly some degree of undress—we know that the book is a “thriller.” When the cover shows a spaceship, we know that the book is science fiction.