I must admit that I have a fondness for H.P. Lovecraft's "revision" stories. These are tales that originally appeared under someone else's name, but the bulk of whose text was in fact written and perhaps conceived by Lovecraft. Amateurs often approached HPL for assistance in getting a story (or stories) polished for submission. Lovecraft usually did this quite willingly, as he was both keen to lend a hand to aspiring writers and because he was regularly in need of funds to support himself, owing both the difficulty he had in selling his own work and how slowly he was paid for the work he did succeed in selling.
Of course, Lovecraft being Lovecraft, he frequently rewrote nearly the entirety of the story he was merely supposed to revise. The result is something that should, in most respects, be considered a Lovecraft story. However, because he took seriously the notion that he was revising someone else's work, HPL did he best to retain as much of his client's ideas as possible, even when, in the final analysis, only the barest skeleton of non-Lovecraftian material can be seen in the revision. Thus, there's generally enough non-Lovecraftian concepts in these revisions to set them apart from the "pure" Lovecraft corpus, which is why some fans turn their nose up at them and treat them as "lesser" works.
I don't feel that way, since, as in the case of "The Mound," the story in question is massive in length -- over 25,000 words -- and filled with terrific Lovecraftian ideas. Written for a client by the name of Zealia Bishop, who lived in Kansas City, "The Mound" was begun sometime in 1929 and completed by 1930, but it did not see print until 1940, several years after Lovecraft's death. Even when it did appear in Weird Tales, it was a much abridged version, which probably contributed to the ill fame in which the story was held for many years. The full, original version of "The Mound" did not see print until 1989, in an Arkham House publication edited by S.T. Joshi and my reading of it a few years afterward convinced me that it is, in fact, a remarkable piece of work, one that ought to stand in the higher ranks of Lovecraft's fiction.
Certainly "The Mound" is no "The Call of Cthulhu" or "At the Mountains of Madness," but it's nevertheless a superb piece of work. It tells of the story of a member of Coronado's 16th century exploration of what is now Oklahoma, named Panfilo de Zamacona y Nuñez. Zamacona had heard tales of an underground realm supposedly filled with great wealth and hires an Indian guide to take him to the entrance to this legendary place. The Indian guides the Spaniard to a huge mound but will go no further, speaking ill of its subterranean inhabitants. Undeterred, Zamacona enters the mound alone, eventually discovering an ancient civilization called K'n-yan.
K'n-yan is inhabited by human-appearing extraterrestrial beings who display amazing mental powers, such as telepathy and dematerialization. Despite these powers, Zamacona finds, to his disappointment, that these beings have fallen into decadence, being unable to operate many of their most impressive pieces of technology, having long since forgotten their principles. Likewise, their morals, once quite sophisticated and subtle, have descended into near-barbarism, with blood sports and other similar entertainments replacing their once-lofty cultural pursuits. Zamacona finds K'n-yan fascinating but, as a 16th century Spaniard, he has no desire to remain there forever. Unfortunately for him, its inhabitants have other ideas ...
"The Mound" is definitely not what one would call a "thrill a minute" story, but then probably no Lovecraft story could be called such with a straight face. It is, in many ways, largely an extensive travelog of an imaginary place, a subterranean world that is both awe-inspiring and horrifying. Lovecraft gives free rein when he describes K'n-yan, which he presents neither as a utopia nor as a nightmare realm. It's clear that some aspects of its society were derived from Lovecraft's own ideals -- its elevation of the rational and the esthetic, for example -- but other aspects were derived from his own fears, particularly his feeling that any civilization not properly guided by its ruling class would inevitably descend into demagoguery and decay.
Perhaps it's for that reason that I like "The Mound" so much: Lovecraft seems a little less prone to idealizing his own preferences here. There's a certain degree of subtlety and nuance in his picture of K'n-yan's decay that I find strangely compelling. Indeed, I prefer his portrayal of these subterranean aliens to his portrayal of the elder things of Antarctica or the Great Race, both of whom lived in more unqualified Lovecraftian utopias. Perhaps I overstate my case here, but I can only say that Lovecraft's writing in "The Mound" comes across as differently than it does in many of his more well-known pieces. That difference may be why many judge it a lesser work and maybe they're even right to do so. But, for me, it's a fascinating example of world building and a reminder that, first and foremost, Lovecraft was a fantasist, not a horror writer, and his ability to create unique and memorable fantasy worlds is a good part of why I still read him.