If you want to to further research into the Cthulhu Mythos, go straight to the source. The following list includes dozens of stories, anthologies, and novels to inspire your games.
The Dunwich Horror and Others (esp. “The Call of Cthulhu,” “The Haunter of the Dark,” “The Dunwich Horror,” “The Whisperer in Darkness,” “The Thing at the Doorstep,” “Shadow over Innsmouth,” “Pickman’s Model,” “The Colour Out of Space,” “The Rats in the Walls” “Cool Air,” “The Terrible Old Man,” and “The Shadow Out of Time”)
Dagon & Other Macabre Tales (esp. “Herbert West, Re-animator,” “The Temple,” “The Hound,” “The Festival,” “Under the Pyramids,” “The Horror at Red Hook,” “The Cats of Ulthar,” and “The Strange High House in the Mist”)
At the Mountains of Madness (esp. “The Statement of Randolph Carter,” “The Case of Charles Dexter Ward,” “The Shunned House,” “The Dreams in the Witch-House”) and The Dream-Quest of Unknown Kadath
The Horror in the Museum and Other Revisions (esp. “The Curse of Yig,” “The Loved Dead,” and “The Diary of Alonzo Typer”)
The Fungi from Yuggoth (sonnet cycle, ideal for use as excerpts of poems by Justin Geoffrey or Edward Pickman Derby); “Nyarlathotep” (prose poem)
The H. P. Lovecraft Dream Book (transcriptions of actual dreams Lovecraft had, some of which he later turned into stones)
Supernatural Horror in Literature (essentially Lovecraft’s own recommended reading list of weird horror)
H. P. Lovecraft’s Book of Horror It not only contains Lovecraft’s treatise, “Supernatural Horror in Literature,” but also contains twenty-one of the stories he mentions in that essay, by authors including Poe (“The Fall of the House of Usher”), Bierce (“The Damned Thing”), Chambers (“The Yellow Sign”), Smith (“The Double Shadow”), Hodgson (“The Hog”), Machen (“The Great God Pan”), and James (“Count Magnus”)
The Dream Cycle of H.P. Lovecraft: Dreams of Terror and Death, The Transition of H. P. Lovecraft; The Road to Madness, Tales of the Cthulhu Mythos. These titles, available from Del Rey in both hardcover and trade paperback, are easier to find than the collections listed above, and contain most of the same stories.
Complete short stories (esp. “Genius Loci,” “The Devotee of Evil,” “The Double Shadow,” “The Return of the Sorcerer,” “The Tale of Satampra Zeiros,” “The Door to Saturn,” “The Vaults of Yoh-Vombis,” “The Plutonian Drug,” “The Empire of the Necromancers,” “The Charnal God,” “The Maze of Maal Dweb,” “The Nemesis of the Unfinished,” “The Holiness of Azedarac,” “The Beast of Averoigne,” “The Enchantress of Sylaire,” “The Mandrakes,” “The Maker of Gargoyles,” “The Colossus of Ylourgne,” “The Disinterment of Venus,” “The Enchantress of Averoigne,” and “Morthylla”) and The Dead Will Cuckold You (play)
The Book of Ethan
Nameless Cults
“The Hounds of Tindalos” and “The Horror from the Hills”
Mysteries of the Worm (esp. “The Shambler from the Stars” and “The Shadow from the Steeple” [the first and final stories in a triptych to which Lovecraft’s “The Haunter of the Dark” is the centerpiece], “Fane of the Black Pharaoh,” and “Notebook Found in a Deserted House”)
Complete short stories (esp. “Cold Print,” “The Insects of Shaggai,” “The Faces at Pine Dunes,” “The Franklyn Paragraphs,” “The Plain of Sound,” “The Moon-Lens,” “The Room in the Castle,” and “The Inhabitant of the Lake”)
“To Arkham and the Stars” and “Terror from the Depths”
The Book of Iod (esp. “The Salem Horror,” “Hydra,” and “The Eater of Souls”)
Nightmare’s Disciple
A Night in Lonesome October
Rules of Engagement, “The Nullity of Choice,” and “The Second Effort”
Songs of A Dead Dreamer, “The Sect of the Idiot,” “The Last Feast of Harlequin,” and “The Dark Beauty of Unheard Horrors”
Scrolls of Thoth Unusual historical fiction featuring Simon Magus as the central character. Mythology and Roman history blend with the Hyborian and Cthulhu Mythos cycles.
The Xothic Legend Cycle
The Trail of Cthulhu, “The Thing That Walked on Wind,” “The Snow-Thing,” “Beyond the Threshhold,” “The Shuttered Room,” “The Sandwin Compact,” and “The Lair of the Star-Spawn”
Alien Intelligence, Bob Kruger, ed. An anthology of short stories showing many different aspects of Delta Green (one of the settings featured in the Settings chapter of this book).
A Cthulhu Mythos Bibliography and Concordance, by Chris Jarocha-Ernst. A terrific resource that lists over 2,600 works by title and author with bibliographical data and a listing of which Mythos terms appear in which stories.
Cthulhu 2000, Jim Turner, ed. This collection of modem Mythos fiction includes stories by eighteen authors, including T.E.D. Klein (“Black Man with a Horn”), Poppy Z. Brite (“His Mouth Will Taste of Wormwood”), Michael Shea (“Fat Face”), Gahan Wilson (“H.P.L.”), and Harlan Ellison (“On The Slab”).
—Encyclopedia Cthulhuiana, by Daniel Harms
—Tales of the Lovecraft Mythos, Robert Price, ed. This volume contains tales from Howard (“The Thing on the Roof,” “The Fire of Asshurbanipal”), Bloch (“Fane of the Black Pharaoh”), Smith (“The Seven Ceases”), Kuttner (“The Invaders,” “Bells of Horror”), Derleth (“The Thing That Walked on the Wind,” “Ithaqua”), and others.
Universally recognized as the greatest writer of ghost stories ever.
Complete ghost stories (esp. “Casting the Runes,” “The Tractate Middoth,” “The Mezzotint,” “A View from a Hill,” “A Neighbor’s Landmark,” “Mr. Humphries and His Inheritance,” “Oh, Whistle and I’ll Come to You, My Lad,” “The Stalls of Barchester Cathedral,” “Count Magnus,” “The Treasure of Abbot Thomas,” “Martin’s Close,” “A Warning to the Curious,” “Canon Alberic’s Scrape-book,” “Count Magnus,” and “Rats”)
The King in Yellow (esp. “The Yellow Sign” and “The Repairer of Reputations”)
Ghost and Horror Stories (esp. “The Damned Thing,” “Strange Disappearances,” “The Suitable Surroundings,” “The Moonlit Road,” “Haita the Sheperd,” and “An Inhabitant of Carcasonne”)
“The Facts in the Case of M. Valdemar,” “The System of Dr. Tarr & Professor Fether,” “A Tale of the Ragged Mountains,” “Ligeia,” The Narrative of A. Gordon Pym (referenced in Lovecraft’s At the Mountains of Madness), “Silence,” “William Wilson,” “Never Bet the Devil Your Head: A Tale with a Moral,” “The Fall of the House of Usher,” and the unfinished “The Lighthouse”
“The Willows,” “The Wendigo,” “Ancient Lights,” and “Entrance & Exit”
John Silence
The Three Importers (esp. “The Novel of the White Powder” and “The Novel of the Black Seal”)
“The White People,” “The Inmost Light,” “The Shining Pyramid,” and “The Great God Pan”
Carnacki the Ghost-Finder (esp. “The Whistling Room“)
Deep Waters (esp. “The Derelict“ and “The Voice In the Night“)
The Ghost Pirates, The House on the Borderlands, The Night Land, and The Boats of the ‘Glen Carrig’
The Gods of Pegana (esp. “The Deeds of Mung,” “A Shop in Go-by Street,” and “Alhireth-Hotep the Prophet”)
Time and the Gods (esp. “The King That Was Not”)
The Sword of Welleran (esp. “The Highwayman,” “The Ghosts,” and “The Fortress Unvanquishable, Save for Sacnoth”)
A Dreamer’s Tales (esp. “Where the Tides Ebb and Flow,” “Bethtmora,” “The Hashish Man,” “Poor Old Bill,” and “The Field”)
The Book of Wonder (esp. “The Hoard of the Gibbelins,” “How Nuth Would Have Practised His Art Upon the Gnoles,” and “Chu-bu and Sheemish”)
The Last Book of Wonder (esp. “The City on Mallington Moor,” “The Bureau d’Echange de Maux,” and “A Narrow Escape”)
Fifty-One Tales (esp. “Taking Up Piccadilly,” “The Sphinx in Thebes [Massachusetts],” “The Trouble in Leafy Green Street,” and “Lobster Salad”)
Tales of Three Hemispheres (esp. “How the Office of Postman Fell Vacant in Otford-under-the-Wold” and “The Sack of Emeralds”); also “The Return”
A Night at an Inn (play).
“Rosa Alchemica,” “The Tables of the Law,” and “The Adoration of the Magi”
“Footsteps Invisible,” “Mr. Dexter’s Dragon,” and “Do You Believe in Ghosts?”
“The Jolly Corner”
Dwellers in the Mirage and The Moon Pool
The Face in the Frost, The House With a Clock in its Walls, “The Spell of the Sorcerer’s Skull,” “The Doom of the Haunted Opera”†, “The Spectre from the Magician’s Museum”†, and “The Beast Under the Wizard’s Bridge”† [†: with Brad Strickland]
The Land of Laughs
The Haunting of Hill House (the ultimate haunted house novel)
Salem’s Lot (The model of how a horror classic, in this case, Dracula, can be updated to the modern day without losing any of its impact.)
“The Book of Sand,” “The Zahir,” “The Circular Ruins,” “The House of Asterion,” “The Aleph,” and “Tlon, Uqbar, Orbis Tertius”
The Borrowers Beneath and “Cement Surroundings”