In the print world titles and Title pages are quite different from headings and carry a different function. They announce to the world what your document is about and also contain such information as the author's name and the publisher.
Book covers Title pages are different from the book's cover.
The book cover is trying to attract a potential readers attention, and its style should also reflect the books contents. A cover of loud, clashing colors probably is not appropriate for a book on Debussy, although it may be so for a book on Wagner. In many ways the books cover is equivalent to the home page of a website. The title page of a book is part of the front matter of the book, which may also contain other pages including a table of contents. A navigation bar is not a substitute for a good table of contents, although it is a good addition to it.