Well, in a book description of fiction, one of the main things is the genre indication. For example, if it's a mystery, it might mention clues or the detective character. Another aspect is the conflict. This could be a person - against - person, person - against - society, or person - against - nature conflict. And don't forget about the theme. It could be about love, friendship, or survival, which gives the story a deeper meaning.
In a book description of fiction, there are several elements to consider. First, the hook. This is what grabs the reader's attention at the very beginning. It could be an interesting question, a shocking statement, or a unique situation. Then there's the narrative arc. It shows how the story progresses from the beginning, through the middle with rising action, to the end with a resolution. Also, the tone of the book, whether it's serious, humorous, or suspenseful, is usually conveyed in the description.
The key elements often include the plot summary, which gives a brief overview of the story's main events. Also, character descriptions are important as they help readers understand who the story is about. The setting, whether it's a real or fictional place, is another key element as it sets the mood and context for the story.