An edition is a particular version of a publication. A book collector will pay a lot of money for a first edition of an important work (but that probably doesn’t include any of the paperbacks on your shelf).
Edition can also refer to a book’s format. If you really enjoy reading a particular book, you might want to purchase a leather-bound, gilded-edge edition of it. In addition, edition can designate a particular issue of a newspaper. If you're a fan of crossword puzzles, you know that the toughest puzzle usually appears in the weekend edition.