The intellectual content in a physical book need not be a composition, nor even be called a book. Books can consist only of drawings, engravings, or photographs, or such things as crossword puzzles or cut-out dolls. In a physical book the pages can be left blank or can feature an abstract set of lines as support for on-going entries, i.e., an account book, an appointment book, a log book, an autograph book, a notebook, a diary or day book, or a sketch book. Some physical books are made with pages thick and sturdy enough to support other physical objects, like a scrapbook or photograph album. Books may be distributed in electronic form as e-books and other formats.