From a reader and prospective buyer's point of view I can only speak for myself. I prefer illustrated cover designs as opposed to those with real people posing on them. What I immediately check out is the book's synopsis. This tells me all i want to know. How well and concise it is written indicates to me whether the author has skills. But the book's subject matter is what ultimately determines whether or not I want to buy it.. A long author's bio that reads like a resume is also a red flag because it is usually more than I want to know. I have had results in unloading books by simply having a few copies readily available for the people who, when they know or find out that I am an author, are curious about this. If they immediately have a copy of the book in their hands and there's chance of getting it autographed, they will buy it if the price is no more than $10.00. Bottom line, I don't think a book cover and a lot of promotion can turn a non reader into a reader. Exposure may catch the eye of avid readers but they still gravitate toward well known authors. Fortunately for me, writing books has never been a profit driven venture. Actually, I guess that's unfortunate for me. LOL