Shadows from Harry’s past return to haunt him.
At first hobbies/preferences and habits/routines are minor details. They offer very little insight about the character, but over time those details can build on each other to create a more well-rounded character. Habits and preferences help to reveal different sides of a character, and build character relationships, as well as enrich scenes with minor self-contained subplots.
One of the longstanding challenges is writing characters who are different from the author. Everyone has a unique identity, and part of that identity is their age, their gender, and their ethnic heritage. In short, how does an author write from the perspective of “other characters”?