- Opopomoz
- Opowieści niezwykłe
- Oppression
- Optifly et l'optimisme 04
- Opération casse-croûte
- Opération Dreamteam
- Opération Jehanne d'Arc
- Opération Léviathan
- ORA'S QUEST
- Oracle of Doom (The Library Book 3)
- Oracles of Delphi Keep
- Orage sur le Val d'Hespar
- Orange Crush
- Orangen und Datteln
- Orbs and Forces
- Ordelanden
- Order of the Undying
- Order of the Wicked
- Orfeo
- Organ Donor
- Origins Of The Magdon: Anthology Collection Of Adventure Novelettes
- Orion's Awakening
- Oro e sangue
- Orphan Ahwak
- Orphan Dreamer and the Missing Arrowhead
- Orphans of the Tide
- Orson's Echoes
- Os Arquivos Perdidos 7: Os legados do Número Cinco (Os Legados de Lorien)
- Os cabelos de Crisálida
- Os Contos de Beedle o Bardo
- Os criminosos vieram para o chá
- Os defensores de Deneb e a espada na pedra
- Os doze trabalhos de Hércules
- Os doze trabalhos de Hércules – vol. 1
- Os doze trabalhos de Hércules – vol. 2
- Os Gatos Detectives Na Península Coreana
- Os Gatos Detetives Na Península Da Coreia
- Os irmãos Tapper declaram guerra (um contra o outro)
- Os Manezinhos em Competição Enigmática
- Os Melaysteiros De Monray
- Os Meninos da Biblioteca
- Os Náufragos de Bornéu
- Os Piratas Circulares
- Os Seres Encantados do Mar
- Os Sete Elementos
- Os tigres de Mompracem
- Os três mosqueteiros
- Os Viajantes
- Os vira-latas do sucesso
- Os Zumbis Telefônicos
- Os Óculos Mentirosos
- Os últimos Heróis
- Oscar Hazelnut and the Metal Dogtectors
- Osgood’S Luck: a Tale of the Grasslands
- Osito Tomás conoce la gran ciudad
- Ostrich Boys
- Ostrov zasvěcení
- Oswald Bastable and Others
- Other Echoes
- Other Worlds
- Othergirl
- Otherworld
- Otherworlds - Tome 1
- Otto and the Hunt for Mal Goue
- Otto of the Silver Hand
- Oufti et le roi Houtsiplou
- Our American Cousin
- Our Australian Girl: Meet Pearlie (Book 1)
- Our Home in the Silver West
- Our Last Summer Musical
- Our Legacy Forever
- Our Little Canadian Cousin
- Our Little Cuban Cousin
- Our Little Dutch Cousin
- Our Little English Cousin
- Our Little Finnish Cousin
- Our Little Hawaiian Cousin
- Our Little Hindu Cousin
- Our Little Hungarian Cousin
- Our Little Irish Cousin
- Our Little Jewish Cousin
- Our Little Korean Cousin
- Our Little Polish Cousin
- Our Little Roumanian Cousin
- Our Little Scotch Cousin
- Our Little Servian Cousin
- Our Little Swedish Cousin
- Our Little Swiss Cousin
- Our Little Turkish Cousin
- Our Market
- Our Monsters
- Our Young Folks
- Out for the Count
- Out of Bounds
- Out of Darkness
- Out of My Heart
- Out of Sync
- Out of the Darkness
- Out Of The Silent Planet
- Out Of The Woods 2nd Edition
- Out of Time's Abyss
- Out on the Drink
- Out on the Pampas
- Out There: Book Four: Earth
- Out There: Book One: Paradise
- Out There: Book Three: TiWat
- Out There: Book Two: Adonae
- Outback
- Outback Heroes (Dangerous Days Series Part 3)
- Outbreak
- Outbreak (The 39 Clues: Superspecial)
- Outcast of the Flame
- Outlander Page
- Outpost
- Outside
- Outside Inside
- Outside the Cities
- Outwalkers
- Outward Bound
- Over the Edge
- Over the Top and other stories
- Overland through Asia; Pictures of Siberian, Chinese, and Tartar
- Overnight Sensation
- Overtones of Midnight
- Overturned
- Overworld in Flames
- Ovily Pumpkin
- Owl
- Owl Hunt
- Ox Cart Angel
- Oz: The Great and Powerful Junior Novel
- Ozland (The Everland Trilogy, Book 3)
- Ozma of Oz (Illustrated + FREE audiobook download link)
- Ozman Grape
- Ozoplaning with the Wizard of Oz