Final answer:
The theme of a book is its underlying message or lesson, which is more complex than a simple moral and binds the narrative's elements to offer insights into life or human nature.
Step-by-step explanation:
The theme is the message, lesson, or moral of a book. When analyzing literature, the theme is seen as the central, unifying idea behind the story, connecting plot points, conflicts, and characters to a broader understanding about humanity, life, or the universe. Unlike Aesop's Fables which clearly state a moral, most literature is complex and contains multiple themes; therefore, reducing a book to a single message often oversimplifies it. The theme provides insight into the author's perspective on the human condition, society, or other broad concepts and should be thought of as more than just the main idea.