Aaron Shepard stubbornly claims simple book covers work best for internet sales, particularly on Amazon. I agree with him to a point. Aaron's covers are super simple and he takes a bit of grief for his covers. His books on self-publishing sell well because he is an expert and the content is valuable and worth the money spent by the customer. Aaron is not going to win any awards for cover design.
I do believe simple covers work best with the small size of the cover photos Amazon provides in the product listings. Complex artwork and design simply does not show up well.
Even with Search Inside, customers will still judge a book by its cover. Detailed product description information, reviews, and tags all play a part in the customer's decision to buy a book. But it seems the cover still plays a role in encouraging the customer to click on the book's product page to examine all of the above items.
I have learned the hard way covers do play a role in this process. My book, Better Basketball Practices, is for individuals who want to plan, organized and conduct more efficient basketball practice sessions. This is actually an important topic for basketball coaches and very few coaches are able to conduct quality practices on a consistent basis. Sales for the book have been poor despite considerable positive feedback via e-mail from the coaches who have purchased the book.
The cover was ultra basic and while I thought the design was fine, The Publishing Maven hated it. In fact, she hated it so much she created a new cover design for me without asking. I simply received an e-mail with two design options attached. My feelings were not hurt in the slightest - male ego can cause you to do funny things - and I promptly uploaded the new cover file with CreateSpace.
The results have led me to believe covers do make a big difference, even for on-line sales. Sales for the month of May for all of my titles are annually either the lowest or second lowest for the year. Sales for this single title this month alone are equal to the total combined sales for this title since October when it was introduced. Anecdotal evidence, yes, but it has gotten my attention. Future releases will require high quality covers and over time and as I can afford it, some of my older titles will get new covers.
And no, Christie does not design and produce covers professionally. She simply created this one cover for me as a favor. Joel Friedlander, the The Book Designer does though.