As much as I have enjoyed most of John Steinbeck's work, I have to say that his To a God Unknown was not much good. It seemed to be Steinbeck channeling D. H. Lawrence, combining the worst aspects of both writers. However, I did enjoy this cover, which was recently included in an ABE mailout.
Lust for land?
Even better is this Corgi cover, which appears to show a young lady experimenting with urinating while standing up.
Here are a few more pulpy Steinbeck covers.