The Mystery of the Dune Font
None of these covers shows "the" Dune font, for me.   The first edition of Dune had a very stylized calligraphy that looked like arabic.  I remember it vividly since my dad had this book in the living room, among others; and when I was learning to read, this was the only cover that I couldn't read at all.  (It was a translation, but with the same cover.)These letters are shown on the wikipedia page about the novel: https://en.wikipedia.org/wiki/Dune_%28novel%29EDIT: The covers of some modern french translations are also incredible.  Just the four letters D U N E, which are exactly the same shape but rotated 90 degrees.  It's an incredibly simple and effective design.