Fritz Leiber wrote two of my favorite horror stories ("Smoke Ghost" and "The Terror from the Depths") and one of my favorite Lovecraftian novels (Our Lady of Darkness). I first read him when I was in grade school, and I bought a used paperback of Swords and Ice Magic, a late entry in his famous Fafhrd and the Gray Mouser swords-and-sorcery series. Leiber was a disciple of Lovecraft, and he's at his best when working the Lovecraftian terrain. He mines the connection between modern architecture and the occult like no other, whether he's talking about Simon Rodia's bizarre and beautiful Watts Towers in "The Terror from the Depths" or the haunting cityscape of San Francisco in Our Lady of Darkness.
Leiber is a writer's writer, with a supple and subtle prose style, an eye for spooky detail, and a pervasive sense of humanity amid the strangeness. The semi-autobiographical hero of Our Lady of Darkness is a horror writer, an alcoholic widower coming off a three-year bender, who starts seeing an otherworldly entity ("the Noseless One") through his binoculars while looking out his window one day. Leiber studs the novel with arcane ciphered texts, pseudoscientific concepts like "paramentals" and "megapolisomancy," and real-life literary adventurers including Clark Ashton Smith, Jack London, Ambrose Bierce, and George Sterling. Leiber is able to take the mundane and imbue it with weirdness, making us reevaluate what we accept daily as "reality." I have never looked at San Francisco the same after reading this book. You won't either.