It doesn’t matter if a book is paper or pixels: Covers matter. We are drawn to images, and the brighter and more appealing the image, the more briskly the book circulates.
But there’s a problem. For many public domain, Creative Commons, and self-published works, no image is available. And so libraries sometimes use totally generic covers—the title of the book with a book or film icon to indicate format, for instance.
But it’s boring and works against the discovery of appealing titles.