When you're standing in a bookstore or a library, what is the first thing you see while searching for the next book you're going to read?
Actually, it's probably the title if the books are lined up on the shelf like they normally are. But the title captured your attention. Will the cover turn you off?
However, if you're looking through a list of novels online, the first thing that will probably catch your eye will be the cover. You've searched for the genre that you're interested in and a page full of images appears before you. It's probably the image of the cover that gets you to click on it.
Whether or not you are a published author, you may not have thought about the cover of your novel/eBook. If you've only been published in magazine articles or anthologies, you (probably) weren't involved in the selection of the covers. If you let your publisher handle the creation of the cover for you, you probably didn't have any say in the creation of the cover and you might not even like the cover they provided, but you have to live with it.
Have you ever picked up a book that has a fantastically interesting looking cover and then read the book and looked back at the cover and wondered which character that is on the cover? Yet through the character descriptions inside the book, none of the characters look that way?
The reason for this is, as an author, it's easy for you to imagine what your protagonist looks like. It's almost murder to find an image of that imagined character. You can spend hours searching for the perfect picture and not find it. Not to do any "free" advertising for anyone, but on three of my covers, neither I nor my designer could find the perfect image, so he took a couple of different images and pasted them together, then actually did some drawing of his own onto the image to get it perfect for me. However, some of the other things on one of the covers do not look like they are described inside the book.
Patience is a virtue. You didn't write your book overnight; don't expect the cover designer to create the cover overnight, either. Unless the designer is an artist and actually draws the cover for you, which will cost a lot, there is a long list of sites online that offer "Royalty Free" images for your covers. Royalty Free does not mean that the images are free. It means that depending on the "terms and conditions" set by the site, you may purchase an image and use it as you need to for your project.
I have searched through several different sites for images to make the covers myself and have found a few sites that I prefer. So far, dreamstime.com is my favorite. I see several advertisements for istockphoto.com, but when I'm looking for something there, I seldom find anything that works for me. When I am getting ready to publish an eBook/novel for myself, I always think about what I want the cover to look like, then I will search these sites for the images that I'm visualizing. Once I did find an image I wanted to use, but it needed some manipulation done to it, so I purchased it and sent it to my cover designer. He was able to create the cover the way I wanted it. There is a site called myecovermaker.com that will allow you to upload your images and place them where you want them, then download the completed cover. It is much less expensive than hiring someone to do it for you. But the quality of the cover will be better if you hire a professional to do it for you because they will have the correct programs, usually Adobe Photoshop, ($699). But there are cover makers that you can purchase also. So there are a variety of options out there.
You want the best looking cover you can get, because if it's not appealing, even if you've written the next "Great American Novel," no one is going to click on it, even though you really "cannot judge a book by its cover."
The back cover is not an issue because it doesn't exist in an eBook. But if you have a printed book, then it requires a very good photo of you, the author, and a great description of the book without giving anything away. Even for eBooks, you need to have that description because they're required for the websites where they're published and that's what will get the potential reader to click on the book.