I wonder if non-writers get the process of world building. I know as a reader, I chalked it off as just “what writers did”. Writers make up worlds. Duh. But, there is more to it than that. World building establishes consistency and consistency adds to the believability of your setting. If you’re writing vampire novels, and in book 1, sunlight is deadly to them, but in book 2, they’re fine wandering around outside at high noon, there’s a problem–unless you provide a darn good reason for the change. Note: “I need it for the plot” is not a darn good reason. Throw in a witch who casts a spell on them. Fine. Or a magic item that protects them. Great. But you can’t just have it kill on Monday and not kill on Tuesday.
But that’s the bleeding obvious part of it. There’s more. And it’s what makes your story yours. There are a lot of books out there, and a lot of writers. Thankfully, all the books are different. If you like paranormal stories, you have a variety to choose from. Vampire books: Do you like them dark? Gory? Angst-y? An action-adventure with blood-suckers? Do you like the vampires to be the good guys or the bad guys—or a mix of each? Maybe you like them funny…or comedic…or even slapstick. You can find any of those, and each is a completely different kind of read.
One of my series features a government agency. Kind of like the CIA…but not. Kind of like the FBI…but not. But what I don’t want it to be is “just like” another author’s fictional agency. The name has to be different. The mission has to be at least a little different. We don’t want to just steal M from Ian Fleming to run the place. Or Moneypenny. Or Q. And yet…I need someone in charge. Someone consistent from book to book. And they need to look the same and talk the same from book 1 to book…whatever. If Sven is a six-foot-four blond Swede with an accent in book 1, he better not be easily blending with the pygmy aboriginal terrorists in book 4 unless he’s also one hell of a disguise expert.
Some of my books take place in a fictional town in the western United States. By book 3, I started losing track of the name of the school principal, the woman who ran the sewing shop, and the name of the hero’s sister’s best friend’s husband. I broke down and made the Dreaded Spreadsheet. (Note: I am NOT a plotter, organizer, index-carder, etc., when it comes to this. But I was desperate.) I started jotting down the basics…heroine, her kids. Hero, his sibling and parents. Heroine’s coworkers (which are cross-overs from their own books, so have the same basic framework of people around them). Hero’s coworkers. Various townfolk. The bad guy. The bad guy’s minions. I look down and I realize I have 92 different characters I’m juggling. No wonder I’m having issues! Yeah, most of them are minor characters and don’t even get names. But, you don’t want to have every secondary character in every book named “Charlie”. Or all of them be a blue-eyed blonde in jeans. Or have every child in every book be a 9-year-old. Readers notice these things.
Part of world building is innate. It’s the writer’s voice, preferences, and knowledge base. The other parts of world building involve interwoven layers of details and craft.