Sometimes the covers of the Hugo winning novels is a nice piece of art and sometimes I'm just left scratching my head. For most of these books there have multiple editions so I'm just going with the images from my editions...
The Best
5. Gateway
How to do an interesting spaceship cover: using distinctive designs and present them against a background that isn't just empty space is a good start. Sure this doesn't really have anything to do with the book but it's an eyecatching design.
4. Startide Rising
This omnibus of Startide Rising and The Uplift War has a cover that features all three sentient species from Earth in an interesting way.
3. Left Hand of Darkness
This was a recent Barnes and Noble edition of the book and I like how it depicts one of the central portions of the book. The tiny figures against the start white really look great.
2. The Snow Queen
There's actually two different versions of the cover to this book that were available in short order. This is the one I like better with the unusual vertical composition that depicts most of the major characters in the book in a way that also reflects their relationships.
1. The Dispossessed
I really like the soft panorama that covers the entire story. I can't put my finger on exactly what I like about it, the use of color appeals to me and the blend of images stand out, but I like it better than any of the other covers.
The Worst
5. Stranger in a Strange Land
This is a stand in for those lazy covers where it takes a good work of art that isn't really related to the book and just puts it on the cover. Where Late the Sweet Birds Sang is similar but I chose Stranger because they went all out and selected Michaelangelo to do the cover. Good art, not a good cover.
4. Dune
This is the image from the first edition of Dune (my copy is the SF book club version) and it is ugly. The mottled red and green do nothing to attract the eye and it just makes the whole thing look like smeared fingerpaints.
3. The Forever War
This is a recent hard cover reissue of The Forever War and it is a hideous image. I can't even tell what it's supposed to be.
2. Downbelow Station
How not to do a space ship cover: have a use of perspective and lighting that rival that of medieval woodcuts. Does that right ring circle something or is it an homage to Escher? The speed lines used with the rockets just makes it worse. An ugly, terrible cover.
1. The Gods Themselves
I used to work in printing and when I saw this cover I honestly thought it was a color separation error. Plain text as a cover is bad; blurred text with weak colors is worse. This is a disaster of a book cover.