A fiction book blurb is a short document, maybe only about 200 words, that hints at the book’s contents while making the reader curious to read more. Typically, your blurb should introduce your main character and his biggest problem, but not reveal any important plot points. It should give some flavor of his world and time period. Your word choice and tone (tone is the mood that your writing sets by the way it sounds) should indicate to what genre your story belongs.
The blurb sells your book on the publisher website, at Amazon.com, or inside book catalogs distributed to bookstores. It is the first thing you see on the jacket flap of a hardback or the back of a paperback. Many new writers believe that someone on the publisher’s staff writes the blurb, but actually it is you, the author. And you wouldn’t want it any other way. Who better than you to care enough to write the best possible blurb for your book?
In a blurb, you want to hint at your story, but not reveal major plot spoilers. You should end your blurb with a tantalizing hint of the trouble into which your poor hero is about to plunge. Some authors conclude their blurbs with a rhetorical question (that is, a question for the sake of emphasis to which you really don’t expect an answer) to engage the reader. For example, “Can Hero #1 overcome his self-doubts and prove himself to his true love?” This practice of ending a blurb with a rhetorical question is becoming clichéd.
What else should you include in your blurb? Sometimes authors include a sentence comparing themselves favorably to a more famous author. Sometimes authors include an actual favorable quotation from another author – in fact, that is also called a blurb and usually appears separately from the book blurb and on the front cover of a book or on one of the inside pages before you reach the copyright page. As a reader, I don’t pay attention to comparisons or one-liner blurbs from other authors, and I have heard that other readers don't either. Anyone can make a comparison. As for a one-liner blurb, if it is from a more famous author at the same publishing group, I have to wonder if the publisher strong-armed the author into contributing it, which lessens its authenticity. Overall, I would advise focusing your valuable blurb space mostly on communicating the essence of your story.
If you have managed to include your hero’s situation and big problem, work in anything else that might make your story unique. For example, you might have written your story based on your personal knowledge of Lakota shamans, the Iraq war, or playing professional golf. Make sure you describe your hero as a Lakota shaman who returned from the war to play pro golf. Or perhaps your novel combines genres such as science-fiction and historical romance for a steampunk feel. Whatever you think is your novel’s strong points should be hinted at in your blurb.