The back cover should be more than a simple description of the book, and should include validation both from endorsements and through information about the author.
The description of the book’s content can be the most difficult part. It needs to do several things: outline the basic premise of the story, create an emotional response, and generate immediate recognition by touching on some universal issue.
While authors can try to write their own copy, usually they have trouble working all that into a single paragraph. They should either hand it to someone familiar with their specific category and market or at least get feedback from fellow writers.
When the description fails in any one of these areas, the back copy will fail to capture readers.
Once you have the description, work on blurbs. Testimonials are very effective. If you look at nearly any book, you’ll find that those with a slew of endorsements actually don’t run anything about the plot or the author on the back cover: it’s 100% testimonials. Authors who have only a few strong endorsements should mix those together with the bio and synopsis for best results.
Finally, validate your experience as an author by including a paragraph about you. Even if this is your first book, tell readers why you wrote this book and a little about your journey while writing it.
If you hit all three of these points, you’ll create copy that sells!