Here are the basics of writing book blurbs.
1. Write your back-cover blurb in present tense and in third person with active, direct language.
2. Quickly summarize the basic plot, but don’t give too much away. Your blurb should indicate what your story is about in general and the central conflict. Avoid long explanations and sub-plots.
3. Introduce main characters by name and give a sense of their personality and motivation. A reader must know the character’s basic motives and any specific elements of their story that help to explain the plot.
4. Indicate the setting of the story in vibrant, interesting language. Let the reader know if your story is set in a very specific place.
5. Leave the reader with some sense of mystery. Often, using questions can achieve this.