Frank Herbert's Dune is one of science fiction's most influential and impactful pieces of literature. The political, religious and ecological themes surrounding the story have helped sculpt future novels for generations. That being said, while it's primarily regarded as hugely important to the masses, there's one equally important fantasy writer who had his own differing opinions on the story -- J. R. R. Tolkien.

In 1966, Tolkien wrote a letter to a man named John Bush regarding him obtaining a copy of Herbert's book. When asked about his opinion, Tolkien gave Bush a cordial but blunt description of what he felt. According to the letter, Tolkien prefaced by saying that he finds it impossible for an author to speak about another who works in a similar subject matter. He then adds, "In fact I dislike Dune with some intensity, and in that unfortunate case, it is much the best and fairest to another author to keep silent and refuse to comment."