“The most important aspect of the worldbuilding [of a good novel] is the every day existence of the characters. Without grounding the characters in the mundane, they will seem disconnected from the narrative. Historical romances generally do well, but writing one requires a metric ton of research. And let me tell you, some historical romance readers are vicious. I’ve seen authors ripped to shreds for fudging small details such as champagne flutes.
There is an industry term for historical romances where the setting is researched very lightly and drawn in broad strokes: wallpaper historicals. Wallpaper historicals fail to deliver the authenticity; their characters often exhibit anachronistic tendencies, such as showing a young woman of a regency period strolling in the park without a chaperon, because she is a progressive rebel or showing an aristocrat who finds a loudly giggling, forward heroine charming.”