"The Whisperer in Darkness" remains one of the most accomplished HPL texts. It is generally classified in the category of "Cthulhu mythos. A wrong. First because HPL and never called her big more ambitious texts in this way. Then because there is never a question of Cthulhu or other Ancient One. We are dealing with pure SF story and not the right mix that HPL was doing with the so-called myth of Cthulhu. But the fact remains that the story is excellent. There Lovecraft demonstrated its narrative talent (the first part is only correspondence, like the "Dracula" Brams Stoker) but also of the depth of his imagination (the creatures Yuggoth fungoides and the prospect of space travel provided to renounce his body condition). Finally, the end is particularly successful, and Lovecraft can exploit the discoveries of his time (Yuggoth indeed is none other than the planet Pluto, which only recently discovered it a few years ago).
An excellent text, so. But I encourage you to read more in terms of the talent of this great writer, even if the story already gives a good overview.