After concentrating on front cover art, I have moved on to back cover art. The back of the book is just as important as the front cover.
This discussion is probably moot if you are publishing only e-books, but I found an entire new world of design for physical books.
The front cover should catch your eye; the back cover should persuade you to buy. Your book back cover text is the foundation for your entire book marketing campaign.
The back copy shows attention to detail.
What you say on your back cover not only has the power to turn your book into a bestseller, it will also:
__ Position you as the obvious expert in your field
__ Get the attention of major media
__ Get you booked as a speaker
__ Help you command much higher consulting fees
__ Leverage your expertise into a lifelong stream of products and revenue
The following are some good articles and advice.
Joel Friedlander: http://www.thebookdesigner.com/2013/05/casey-demchak-back-cover-copy/
Watch my Pinterest page. A picture tells a thousand words. The new Harry Potter back cover is really fun. http://www.hypable.com/2014/08/05/harry-potter-uk-back-cover-art/