In the old days, an artist was hired to paint a cover image. He (usually he) was not sent the whole manuscript to read. Instead, the editor chose a few paragraphs, and sent that page along.
The result could be bizarre, rampant sex scenes decorating the cover of many a staid and seemly book, but the idea was to propel sales. Which it undoubtedly did, even if the buyer ended up very surprised at what he or she finished up reading.
Now, artists are out, and stark, iconic images are in. Clarity is now the rule, and the thumbnail reigns. As Emily Condlin points out, the jacket that looks tremendous on a coffee-table book when it is on display in a bookstore can be diminished to near-invisibility on the Amazon page, and so the designers have had to adapt.
As she says, "A great book cover should be striking, memorable, profound, and, most of all, eye-catching. It should pull a reader across a bookstore with a flash of color or a slick effect. But today, designers must think beyond the physical bookstore and consider the digital one as well."
And that means thinking about thumbnails. Somehow, the thumbnail the buyer sees on the Amazon page (or whatever online store) must be as compelling as the cover on the full-sized physical book.
When I was composing the "Publishing your novel on Kindle" blog -- which is a formatting manual for Indie authors -- I found out the true magic of the powerpoint program. This was because of a really nifty website that described a revolutionary and miraculous method for creating a jacket with powerpoint, created by William King and called "Creating your own eBook cover, step by step, with pictures."
The method, apart from being incredibly easy, also has the huge advantage that throughout the process of creating your cover you can see a thumbnail to the left.
Interested? Here are my easily followed step-by-step instructions.
Something else you have to watch out for is the lines of promotional text that were (and still are) commonly found on the covers of printed volumes -- quotes from famous authors, reminders that the author is a best-selling name, and so forth. These look great in the bookstore, and certainly help sell the book. On the thumbnail, however, the words are illegible. They are much better set in text accompanying the book description -- and so it is becoming more and more common to see these blurbs on the back of the jacket, instead of the front.
But why not have one cover for the print edition, and another for the eBook? Not a good idea, according to the wise Emily. As she says, "The cover is the most obvious consumer-facing branding of a book, and designers want to ensure that a reader can recognize that brand across all formats and platforms. Whether a reader sees the cover in a promotional email recommending the book, in the window as she passes her local bookstore, or online when she goes to buy it, she should see the same image every time. The consistency bolsters her relationship with the book and increases the likelihood of purchase."