Since H.P. Lovecraft's popularity was rekindled in the late 1960's, a cult following has grown up around his stories of "cosmic horror". Tales like At the Mountains of Madness, The Whisperer in Darkness, and The Shadow Out of Time, all had horror elements, but many could be more properly called science fiction.
Along with Donald Wandrei, August Derleth championed Lovecraft's work, especially after his death in 1937. The publishing company known as Arkham House was formed, and readers were allowed the luxury of seeing all of Lovecraft's works collected in book form for the first time since they had been published in the pulps.
Derleth himself contributed many stories to what he dubbed The Cthulhu Mythos, a term meant to associate a number of Lovecraft's stories into a loose group of interrelated stories tied together with the concept of a pantheon of god-like beings who were the real overlords of the earth. In truth, there was nothing "god-like" -- in a religious sense, anyway -- about Cthulhu, Azathoth, and Nyarlothotep, who were always waiting at the portal of our world to cause all sorts of chaos and mass destruction on the most elemental and secular of scales.
With a theme like this, its hard not to imagine a cult following developing around the concept of The Great Old Ones and company. Assertions from the interesting to the ridiculous cropped up as a result of speculation behind the "real" meaning behind Lovecraft's stories. Some have even gone so far as to say Lovecraft was a sort of Nostradamus of UFOlogy, predicting our bleak future albeit without the hope that H.G. Wells gave us.
In the 1980's, the "All Evil" issue of CRITIQUE A Journal Questioning Consensus Reality, author Ben G. Price explores the concept of evil in Lovecraft's so-called Cthulhu Mythos.