"Don't judge a book by its cover."
However, we like things that look nice and we often judge on the outward. Books are no exception. So you would hardly want to sacrifice on this area of your work.
When we design our covers, we take into account the nature of the work. We don't do standard templates - each project is drawn up from scratch and with your consultation to ensure that the finished product is something that you're happy with and that meets your expectations.