The author's message refers to the main idea or theme that an author wants to convey through their writing. It is what they want readers to understand or take away from their work.
Related terms
Tone: The attitude or emotion conveyed by the author towards their subject matter.
Purpose: The reason why an author wrote a particular piece - whether it is to inform, persuade, entertain, etc.
Audience: The intended group of readers for whom the author wrote their work.