I'm in the process of getting a series of books published and it's crazy how many details there are in what appeared to be a pretty simple path. One thing that has been a bigger stumbling block than I had planned for: the ebook cover.
How the image appears in a thumbprint on Amazon's website is very important, and has very different demands than an eye-catching book cover on a shelf or table at the local brick and mortar.
Very Different.
Here's a great blog post that not only discusses these differences but gives some nice covers as examples, with a critique of them:
15 Ebook Covers: Success and Failure in the Kindle Store by Joel Friedlander at The Book Designer.