“A picture is worth a thousand words”
“A picture is worth a thousand words” is an English idiom. It refers to the notion that a complex idea can be conveyed with just a single still image or that an image of a subject conveys its meaning or essence more effectively than a description does. When someone looks at the cover of your book you want it to say just as much.
Make your ultimate sales pitch to your reader with a strong statement on your book cover. If they are never enticed to pick it up, they will never read it!