I'm going to be very honest for a few paragraphs. I'm a sucker for a good cover. I have often picked up a book because of its cover, but I only buy a book when the back blurb really catches my attention. And if the cover is good and the blurb is enough to pique my interest but not enough for me to spend money on, I write it down and get the book from the library.
So I don't judge a book by its cover, but I certainly am lured in by good artwork and presentation. Which means that this is something every author should be concerned about. If you are publishing traditionally, then your publisher will probably take care of it. I've heard horror stories about badly done covers that have significantly hurt book sales. I've also seen covers that blow me away. So like anything in life, it can go either way. If you're indie publishing, then spend the money to at least get a respectable cover. Go for a level above that. You won't be disappointed.
Personally, covers give me an idea of what sort of feel I can expect from the book. It should evoke emotions from me, and if I like the combination it presents, then I'll pick it up and look at it.
I'll only bore you with one example. Below is the cover to Time Riders. I picked this one up off the shelf because of the cover. These were my reasons:
-The title has time in it, which means time travel! I was thinking Quantum Leap
-There is a city with a zeppelin in the background, and zeppelins are always cool.
-The whole picture looks a little warped—a little off, which is what I assumed the characters would be fighting against.
-There are three characters pictures. This is a YA book, which means they are a team of some sort. I love a good team story.
This combined my love of light sci-fi with comradeship and time travel, leading me to buy it.
And that's how I use a cover when I buy a book. Notice that the title came into play as well. The blurb didn't do much for me this time around, but sometimes they really draw me in.
What about you? What role does a cover play when you're looking for a new book to read?