I came across this article about how the digital age, Amazon, etc. has changed book cover art in the publishing industry (which is itself changing quite a bit). I’ll let the article speak for itself which you can read here
Over the years I’ve known a number of 3D artists who ended up doing cover art for various books and still do so. The above article makes a good point for artist to keep in mind when creating that cover art. After reading the article I found myself wondering if in some cases an artist might need to create two or even three art images for a single book. One piece as cover art for print publication, possibly a second for eBook publication and potentially a third as a thumbnail for digital catalogs such as Amazon and other online retailers. That would mean convincing publishers and authors to pay for that additional artwork, but its worth thinking about and the article outlines why such additional art could be important to sales.
So if you’re an artist doing cover art or an indie writer making cover art choices, give the article a read and take a look at some of its embedded links. Food for thought.