Thing is, the cover of Gatsby is just about as famous as the text itself. It’s a special case.
The CURRENT cover of Gatsby, as I said there have been many https://www.google.com/search?q=gatsby+cover&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=vPB6UZe4DYb9iQKmnoH4Dg&biw=1133&bih=665&sei=vvB6UdrcOO75igLFuYHwDg . It’s not a special case, it’s a book cover. Whenever a movie gets made of a book there’s a movie tie-in cover, it’s part of the industry.