We are all told that we must not judge a book by its cover, yet I firmly believe we all do it, whether we are using the phrase metaphoically or literally, the outward appearance of an item, is important. I am particularly thinking of book covers when I say this, but it applies just as easily to clothes, cake and cats.
However, let me return to books, and their covers. When I was first published one of my editors told me that the job of the cover art is to get the customer to pick up the book. The job of the back cover blurb is to get them to open it. Your job, as the author, is to write a first page that makes them turn to the next one. If that happens, you've sold a book.
I mentioned this in a recent conversation at Dundeed University Student's Association about cover art, and the delegates agreed that they had never bought a book with a cover they considered to be ugly.
One publisher even told me that they found in their research that covers do even more heavy lifting than that. They have a major impact on whether a reader who read and finished the book will recommend it to someone else. This is critical to an author because a word of mouth recommendation is the best they can possibly get.
Some readers even admitted to being ashamed of recommending books with ugly covers. That last bit of info is definitely something to note, as more and more authors work independently and with small presses. Make sure, whatever you do, that your book will be favourably judged when potential readers look at the covers.