Never judge a book by the cover! Yeah, right. For those who are indie publishing, your cover is the most vital bit of marketing. Don't believe me? I can prove it.
I recently changed a cover of one of my short story collections that hadn't been selling at all. It was ranked somewhere in the 300,000 on amazon.
After the cover change, I've sold more than I'd ever sold of it before. So if your book isn't selling on amazon, change the cover. If that doesn't work, change the description, and then consider a change in price. Who knows what that magic factor is that rockets your book up the rankings, but I will tell you this, it won't get there with a crap cover.