"There are no second chances,

               for first impressions."

Creating a look all your own just before launching your book live to the world is the cherry on top of the milkshake.  
The milkshake wouldn't be half as tempting if it didn't have that 
gorgeous plump cherry just waiting to be devoured resting temptingly atop
fluffy white whip cream.  

A well designed cover on a book should draw the eye of a potential reader, 
make a silent statement, and compel them to sample it - reading the book description, flipping through a few pages.