Don't get me started on Lovecraft. That man was a genius and easily one of the most underrated and original writers of all time. Like the op mentioned, At the Mountains of Madness and Call of Cthulhu is great, and I also particularly love Shadow over Innsmouth and Shadow out of Time. I can't think of any author (or any media director) that can seamlessly fuse Sci Fi, Fantasy, Mystery, and Horror among other things into original stories. Not to mention the original and super cool species he would invent like Yith and Shoggoths. I also really loved a video game adaption of some of his stories called Dark Corners of the Earth, which sadly never saw its sequels and did the books justice. So in short, best author ever in my book.
