Who Goes There? is actually the shortened revision of the story. The original version, titled Frozen Hell is 45 pages longer. It was discovered among Campbell's papers at Harvard and has been released as an
ebook.
Opinions are split on whether the extra pages add or detract from the story. It's likely a wash. Still, worth a look.
Alan Dean Foster wrote a well regarded
novelization of the John Carpenter movie. Unfortunately, it is not *legally* available as an ebook.