I can't really speak to the quality of the science fiction version, as I've only ever read it once and that was some time ago. The weird tales version, however, is a story to which I return regularly -- not because it's particularly good but because I simply adore the idea of round robin stories and see in them something of a parallel to the way many roleplaying campaigns are run. C.L. Moore begins the story by introducing George Campbell who, while camping in the wilderness of Canada, comes across a "queer, smooth cube" as "clear as rock crystal" that is "about four inches in measurement over each worn face." Much as I love Moore's writing, particularly her Northwest Smith stories, I can't honestly say that she does herself much credit in her contribution to "The Challenge from Beyond." Moore does little more than establish an enigma -- the queer crystal cube -- and devotes the rest of her part to musing about its age and origin and how it troubles Campbell's sleep with its luminosity.
Abraham Merritt, alas, does little better than Moore. His follow-up contains some rather amusingly melodramatic prose -- "He felt a chill of spirit, as though from contact with some alien thing. It was alien, he knew it; not of this earth. Not of earth's life." -- but Merritt does at least advance something of a plot. Campbell finds himself drawn into the cube, his ultimate destination left to Lovecraft to describe, which he does in the third part, which is easily three times as long as any other author's contribution. In it, HPL plagiarizes from himself, specifically from "The Shadow Out of Time," by suggesting that it is not Campbell's body but merely his mind that is transported through the cube, exchanging places with that of an alien being that comes to inhabit his human body back on Earth. The alien being is a centipede-like thing, whose civilization explores the galaxy by means of such metempsychosis such as Campbell has now experienced, the realization of which causes the protagonist to faint into unconsciousness.
Robert E. Howard's follow-up is delightful, if only because the turnabout he introduces into the story. Quickly recovering from the delirium brought on by realizing that his mind now inhabited the body of a centipede, Campbell decides to make the best of his situation:
What was his former body but a cloak, eventually to be cast off at death anyway? He had no sentimental illusions about the life from which he had been exiled. What had it ever given him save toil, poverty, continual frustration and repression? If this life before him offered no more, at least it offered no less. Intuition told him it offered more -- much more.It's completely ridiculous, of course, but joyously so. Conan the Centipede! I honestly think, of all the authors involved, Howard acquits himself the best, as he clearly had fun with his segment and did much to liberate it from the plodding and introspective qualities Moore, Merritt, and Lovecraft had saddled the story with up until that point. Long concludes the tale by having Campbell become a veritable god among alien centipedes, never once regretting the happenstance that enabled his mind to free itself from the bounds of Earth.
With the honesty possible only when life is stripped to its naked fundamentals, he realized that he remembered with pleasure only the physical delights of his former life. But he had long ago exhausted all the physical possibilities contained in that earthly body. Earth held no new thrills. But in the possession of this new, alien body he felt promises of strange, exotic joys.
A lawless exultation rose in him. He was a man without a world, tree of all conventions or inhibitions of Earth, or of this strange planet, free of every artificial restraint in the universe. He was a god! With grim amusement he thought of his body moving in earth's business and society, with all the while an alien monster staring out of the windows that were George Campbell's eyes on people who would flee !f they knew.
Let him walk the earth slaying and destroying as he would. Earth and its races no longer had any meaning to George Campbell. There he had been one of a billion nonentities, fixed in place by a mountainous accumulation of conventions, laws and manners, doomed to live and die in his sordid niche. But in one blind bound he had soared above the commonplace. This was not death, but re-birth -- the birth of a full-grown mentality, with a new-found freedom that made little of physical captivity on Yekub.
As I said above, "The Challenge from Beyond" is, even by the standards of pulp fantasy, a poor tale, with one redeeming feature: it's an example, however flawed, of diverse writers working together to produce something that, in total, no one of them would have written but that draws on, to varying degrees, the contributions of all. That's my ideal for a well-run roleplaying campaign; it's what I strive to attain. Like "The Challenge from Beyond," most RPG campaigns are uneven in quality and tone, but that's inevitable when there are several "authors" who don't act according to a plan. On the other hand, that unevenness can sometimes lead to surprising, delightful places, such as Howard's transformation of George Campbell into an insectoid conqueror. I personally think such unexpected turns are worth the price of unevenness, which is why I have such a fondness for "The Challenge from Beyond." It's not great by any measure but it is fun -- just like RPGs.