- Olhando para o Futuro
- Oliver's Hunger
- Olivers Versuchung
- Olivia's Field
- Ollie
- OLTRE
- OLTRE - Alice
- OLTRE 2
- Oltre i confini: Il canto delle Forze Ancestrali
- Oltre i confini: Il tocco degli Spiriti Antichi
- Oltre la Montagna
- Oltre la notte (eLit)
- Oltre ogni regola
- Olympia Investigations: The First Four Cases
- Olympus—of Gods, and Men
- Omaha Stakes
- Ombra tra le ombre
- Ombre
- Ombre e tenebre
- Ombres
- Omega
- OMEGA Born
- Omega Days - Die letzten Tage
- Omega Days - Schiff der Toten
- Omega Mine
- Omega Queen - Box Set Books #1-3
- Omega's Choice
- Omega's Onslaught
- Omega: La fine è solo il principio
- Omega: Momenti perduti
- Omnigalactic: The Eye of Shen'roth
- Omnigalactic: The Fangs of Z'et
- Omnihumans: Within A Concrete Labyrinth
- Omnipotent Blood
- Omnipresent Occultation
- Omniverse: Book I of the Omniverse Chronicles
- Omvänd (Bok #1 i Vampyrjournalerna)
- On a Witch's Mind
- On Eagles Wings
- On Hallow's Eve
- On Holiday with an S.O.B.
- On Loan: A Reading Under Wraps Short Story
- On My Way
- On the Cards Book Four
- On the Cards Book One
- On the Cards Book Three
- On the Cards Book Two
- On the Cards: The Complete Series
- On the Edge
- On the Edge of Destiny
- On the Edge of Eternity
- On the Edge of Humanity
- On the Evil Scale
- On the Hunt
- On the Hunt for the Wizard King
- On the Path of Outcasts
- On the Prowl
- On the Prowl
- On the Rise
- On the Rugged Hills
- On the Street Where Death Lives
- On the Third Night
- On the Wings of a Crow
- On Unfaithful Wings
- Once a Greech
- Once a Predator
- Once an Angel
- Once Awakened
- Once Bitten Twice Smitten
- Once Hunted, Twice Shy
- Once Upon A Coven
- Once Upon A Dragon
- Once upon a ghost
- Once Upon a Multiverse
- Once Upon a Murderous Retreat
- Once Upon A Princess: Land of Dreams
- Once Upon a Snowy Moon
- Once Upon A Sultan
- Once Upon a Time in Peter's Special Book: From "Short Cuts", a short story collection
- Once Upon A Time — Volume 1
- Once Upon A Time — Volume 2
- Once Upon A Time — Volume 3
- Once Upon A Western Way
- Onder Vuur Liggen
- Ondina
- Ondragon 1: Menschenhunger
- One Bite Stand
- One Bite To Passion
- One Bite With A Stranger
- One Dark Summer Night
- One Dead Vampire
- One Enchanted Evening
- One Evening on the Pier
- One for Sorrow
- One For Sorrow
- One for the Wicked
- One Good Turn
- One Hex of a Wedding
- One in the Hand
- One in the Oven
- One Last Quiche
- One More Bite Book Four
- One More Bite Book One
- One More Bite Book Three
- One More Bite Book Two
- One Night
- One Night in Hell
- One Night with a Bear
- One Night with the Shifter
- One Night With The Valkyrie
- One Night With The Wolf
- One Not of the Blood
- One Of The Enemy (Hidden Descendant Series, Book 1)
- One of the Smarter Ones
- One Part Human
- One Rotten Apple
- One Second
- One Silent Night
- One Small Bite
- One Stiletto in the Grave
- One Wish: A North American Pack & Half-Blood Princess Christmas
- Ong's Hat: The Beginning
- Oniria
- Only a Shadow
- Only Child
- Only Forever