- Oona: A Fairy Tale
- Oowans – Curse and Salvation
- Op ons kunt u bouwen
- Open Wounds, A Novella of Beginnings
- Opening Night of the Dead
- OPERATION ANTARKTIKA
- Operation Juggernaut
- Operation Razmer
- Operation Z-Day (The Raven Falconer Chronicles: Episode One)
- Operation: Blackheart
- Opferreigen
- Ophis
- Opowiadania
- Opowieści nadzwyczajne (Tom I/Tom II)
- Oppositional
- Oppositum
- Oppvåkningen
- Opt Out
- Optical Delusion
- Opus
- Opus Secunda
- Ora pro nobis
- Oracles and Miracles and Zombies
- Orange Lake
- Orbital Decay
- Orbs of Avalon: Tales of Urban Magick and Horror
- Orco Rosso: A Dark Novel
- Ordeal
- Order of the Dragon
- Ordinary Souls
- Ore Contate
- Oremor Island
- Oren (Tales from the Island)
- Orfanato Dos Sonhos
- Organ House
- Orgonomicon
- Orgueil et préjugés & zombies
- Origami
- Origin of the Vampyre: A Companion to Doctor Polidori's The Vampyre
- Original Sin
- Original Vampires Ancient Map
- Origins of Evil
- Orlin Wood
- Oro - Un Racconto Breve
- Orotund: Collected Short Stories Volume Two
- Orphan: Sounds Of Evil
- Orphans of Wonderland
- Orrore Antigas
- Os condenados
- Os Contos Do Caso Abraham
- Os contos estranhos
- Os Curiosos
- Os Dançarinos do Ataúde
- Os Dançarinos do ataúde
- Os Fantasmas do Espelho
- Os justiceiros
- Os Limites de Holly Field
- Os melhores contos de Edgar Allan Poe
- Os Melhores Contos de H. P. Lovecraft - 4º vol.
- Os Qontos Dos Infernos
- Os Reis Imortais. O Tormento do Amanhecer.
- Os vários mundos habitados segundo o judaísmo místico
- Oscura salvación
- Oscura signora dell’abisso
- Oscura salvación
- Oscura signora dell’abisso
- Oscure presenze
- Oscuri Segreti
- Oscuro reflejo
- Osgood Riddance: A Spectral Inspector Novel
- Ostrov Duma Key
- Osvícení
- Other Kingdoms
- Other Lives
- Other Stories
- Oto
- Otra vuelta de tuerca
- Otro cuento de Navidad
- Our Dead Bodies
- Our Endless Numbered Days
- Our Father Who Art in Middle Management
- Our First Kill: A Where Shadows Fall story
- Our Lady of Pain
- Our Last Day
- Our Living Funeral Stories of Horror
- Our Lord Weathercock
- Our Miss Engel
- Our Monsters Are Real
- Our Other Blood (Lion of the Dark Series)
- Our Undead
- Ours
- Out After Dark
- Out for Blood
- Out For Blood
- Out of Body