But my book is set in the 1920’s. The real 1920’s. No need for world building, right?

Wrong.

One of the most important parts of sci fi and fantasy world building is deciding on “the rules of the world.” If you decide that wizards and witches generate their power by chowing down on the legs of spiders dipped in tabasco sauce… well, weird, but ok. It’s a rule. You establish it early, and you’re expected to stick to it for the remainder of the story.

In more reality-based genres, a lot of the technical rules have already been established (the sun rises in the east and sets in the west). But I still have to answer some metaphysical questions about the way my world operates. Such as:

• Do bad things happen to good people?

And if so, how bad? Is my world one in which an innocent woman could be kidnapped? In which she could be raped and killed? In which a child could be raped and killed? Or is it a world in which, in general, if something awful happens to you, you deserved it?

• Does true love conquer all?

Most romances would answer this question in the affirmative; so many that I’d say it’s an underlying rule of the genre. For other genres, it’s not always such a clear answer.

• Does everyone get their just desserts?

Is justice a sort of force in my world, one which just can’t be denied (no matter how much it seems like it can deep in the middle of Act II)? Or is justice only for a certain part of society, those that can afford it? What about injustice? Are there forms of it that are rampant, expected, part of the cost of living in this world?

• What are the roles of various groups?

Are the cops generally the good guys or the bad guys? Are politicians crooked or honest? Are women independant or helpless? Are children innocent or cruel?

• What is the role of accident and coincidence?

Is it acceptable to have the plot turn on an accident? Or is everything the result of carefully orchestrated events?

• What kind of humor exists in my world?

Is it at all possible that my protagonist will slip on a banana peel? Can her character be wildly over the top? Or is my world a grittier, realer place where humor consists mostly of bitingly clever dialogue?

No matter how factual the setting, I have a lot of leeway to play with all of these things. And I have an obligation to keep all of them consistent. Otherwise, I’ll get the same reaction as the fantasy writer who suddenly has her wizard draw power from eating butterfly legs dipped in ketchup:

WTF?