Or if you rock the planet like Kristin Cashore...
(Go here to see her entire book gallery.)
And many more (just type in "cover wars" on KM's blog search and you will see an entire list.)
I find the hardcover vs. paperback changes to be the least desirable. Why the drastic change? I assume publishers think the different cover art will appeal to a whole new audience. For some reason I have an affinity towards the cover of the book I read. Like The Forest of Hands and Teeth by Carrie Ryan, I prefer the hardcover because that's the physical copy I read. I'm even picky as to which addition I share on my Shelfari or Goodreads bookshelves.