People do judge a book by its cover. The biggest challenge you face is getting readers to pick up your book (or click on a thumbnail) long enough to read the blurbs, reviews, or other promotions. The cover is the first thing they see and it's the most important marketing tool you have. It has to entice enough interest in a single glance to get readers to stop and take that second look. A good cover will do just that, and getting your book in their hands is more than half the battle.