While it is true that no book is the same, there is a certain formula that novels follow that can be found in almost all fictional literary work. Novels come with a setting (where & when), plot (what), characters (who), and theme (why).
The setting of a novel is the where and the when. All books take place somewhere. The setting can be the world, country, city, town, house and room. Setting also will designate the time. When does the story take place?
Depending on your genre, setting can be simple or hard. Sci-Fi and fantasy writers will have to create whole new worlds and populate it with various races and/or species. Whereas a person writing a mystery novel merely needs to be familiar with the area the story takes place in. In this instance, it’s a good thing to write what you know. Have you ever noticed how Stephen King likes to write stories that take place in Maine? That’s because he knows a lot about it. Write what you know.
In addition to location, you need to know what time or era your book takes place in. This is important so that you are chronologically accurate. You don’t want your 1950s detective having an iPod. For the fantasy writers, you will need to decide the time period of your story. Are you using a medieval/Renaissance type period? How about a time period where they are more technologically advanced?
Setting and worldbuilding is an important step in drafting your bestselling novel. Even if the details aren’t written in the book, you (as the author) should still know them.