RedT Reads Randomly

 for other Cover Love, check out Hunger For Knowledge's Draculas and Carpe Librum's Sunne in Splendour .  ETA: 20,000 Leagues Under the Sea By Nostalgia Reader; and Mayor of Casterbridge by Books, Hockey, and a Bucketful of Snark

 Wizard of Oz was one of my childhood favorites.  It has been published under both titles: Wizard of Oz, and The Wonderful Wizard of Oz.  Here are several covers featuring illustrations by the original artist, W. W. Denslow:

ETA:  this one mentioned by Hyzie, aka Primrose, in the comments:

The pages are Emerald City green.

And several from the movie:

The story has inspired other artists over time who have added to the repertoire:

I love these gorgeous art-deco inspired covers:

Also these very contemporary ones:

These emphasize symbols:

And here are some specialty covers:

 Both of the next two highlight the objects of the quest: brain, heart, courage and home.  

I liked this one quite a lot:  

but this one's kind of terrible: 

 It's kind of funny that, although the book describes the slippers as silver, the movie's portrayal of them as ruby seems to be the image that has stuck:

  . 

There're about a million other book covers out there; some amazing, some very crappy.

these are among my favorites. (Except that one, up there with the brain.)