Howard Phillips Lovecraft is my favorite writer in the "Weird Fantasy" genre, which he shares with such writers as Edgar Alan Poe and Shirley Jackson. Lovecraft's books tend to be hard to find in bookstores, which is a shame, because his tales are fascinating and engrossing. He is truly one of be best writers of his genre.
Lovecraft's specialty in the early part of his career was Dream Quest Fantasy. His early masterpiece The Dream Quest Of Unknown Kadath is the crowning glory of this genre. Other than three paragraphs on pages 1 and 2, and a half a page at the end, the entire novel takes place in the world of dreams. In light slumber, Randolph Carter descended the 70 steps to the cavern of flame and spoke with the bearded priests Nasht and Kaman-Thah. He then boldly descended the 700 steps to the Gate of Deeper Slumber, and set out through the Enchanted Wood. On his journey through the dreamlands, he meets zoogs, moon beasts, night gaunts, dholes, ghouls, ghasts, gugs, and myriad other creatures. He descends to the unhallowed bowels of the earth, wherein lies the vale of Pnoth. He sails colorful barqs down rivers through perfumed jungles and forests. He passes golden temples, glowing in the afternoon sunlight. He flies across the desert wastes north of Ooth-Nargai with an army of ghouls and night gaunts. Eventually he reaches Kadath and the onyx castle of The Great Ones themselves, and faces Nyarlathotep, aka "The Crawling Chaos", who sends him on a horrifying journey, on the back of a hideous shantak bird, to the center of the universe, where the final horror awaits him which threatens to destroy his mind and soul. Altogether, this is the finest Dream Quest Fantasy I have ever read.
Later in his career, however, the tone of Lovecraft's work became more dark, spooky, and horrifying. Most of these later tales take place in the waking world rather than the world of dreams. Many of these tales involve -- directly or indirectly -- the creature named "Cthulhu", who was first mentioned in the short story "The Call of Cthulhu", and hence that period of his writings is called "The Cthulhu Mythos". ("Cthulhu" can be pronounced either "Kthul-hu" or "Sthul-hu", as you like.) Some of my favorite tales from this late period of Lovecraft's writing are the short stories "The Call of Cthulhu" and "The Haunter of the Dark", and the novels "The Dunwich Horror" and "The Shadow Over Innsmouth". But be warned: these tales will give you uncomfortable nightmares if read at midnight!