A book’s style sheet is the foundation of its style. Sometimes begun at the substantive editing stage, but more often at the copyediting stage, a style sheet is a comprehensive list of any style choices made by authors and editors. These choices include choices regarding dictionary and style guide (for example, the Chicago Manual of Style or The Associated Press Stylebook or Garner’s Modern American Usage) as well as words, terms, and usages. If your book uses the serial comma in Chapter One, the style sheet ensures that the serial comma will be used without, ensuring consistency and clarity. A style sheet makes certain that your main character, known as Dragonslayer in her youth, won’t be called Dragon-Slayer in her adulthood, and that her sidekick’s nickname won’t grow an extra letter somewhere along the way.
I freely admit to being a style sheet nerd — my style sheets are my pride and joy. A good style sheet is crucial to polishing a book as well as ensuring that the book’s author, copyeditor, proofreader, and designer are all (sorry) on the same page.