If you can’t relate to a character, can you understand them? Sympathise with them to an extent? This is particularly true of an antagonist. Backstories can provide this context. They give the reader reasons behind the character’s actions and are most effective when information is used sparingly, and when it is most relevant to the story.

For example, if something prompts a flashback. This is where the narrator relates the relevant information to another character or the reader. It can be as little as a throw-away line, the significance of which is only apparent later in the book or series, or a more detailed recollection. The information can completely recontextualise everything we thought we knew so far about a character and provide hints of what’s to come in the book through foreshadowing.

Backstories and foreshadowing keep the reader invested in the story, knowing those questions raised by the author will be answered and the reader can use their existing knowledge of the book and characters to infer those answers.