Sophie’s World by Jostein Gaarder

Sophie Amundsen, a 14-year-old girl in Norway, begins receiving mysterious letters posing deep philosophical questions like “Who are you?” and “Where does the world come from?” These messages lead her into a secret philosophy course taught by Alberto Knox, who guides her through the history of philosophy—from the Pre-Socratics to modern thinkers like Marx, Freud, and Sartre.

As Sophie learns more, she uncovers a mind-bending twist: she and her world are part of a book written by a man named Albert Knag for his daughter, Hilde. Sophie and Alberto attempt to break free from their fictional existence, blurring the line between reality and imagination.