- Only a Mother Knows
- Only an Ensign: A Tale of the Retreat from Cabul (Complete)
- Only an Incident
- Only Beloved
- Only Call Us Faithful
- Only Charlotte
- Only Death
- Only Time Will Tell: the first six chapters
- Only Until I Need Glasses: The Extraordinary Life and Adventures of Jimmy DeAngelo
- Only Words: A Fairy Tale
- Only Wounded
- Onnen Visser, der Schmugglersohn von Norderney
- Onore scozzese (eLit)
- Onslaught: The Centurions II
- Onstage Violence in Sixteenth-Century French Tragedy
- Onto The Third Generation
- Onward Virgin Soldiers
- Onzaligen van Lódz
- Op'n Padd bröcht
- Opa, du, …?
- Opal
- Opal’s Journey
- Open Country
- Open Earth, Open Doors
- Open Fields
- Open Hands
- Open Heart: A Poignant and Gripping Historical Novel about the Enduring Power of Love
- Open Secrets
- Opened Ground
- Opening Day, 1954: A Short Story
- Operación fuego mágico
- Operación Gladio (Los casos de Juan Urbano 2)
- Operación redes (regreso al desierto del Sahara)
- Operación triángulo. El misterio de Pi
- Operation Alfur
- Operation Black Eagle
- Operation Blue Sapphire
- Operation Broadsword
- Operation Citadell
- Operation Falska bevis
- Operation Felix
- Operation Hot Gates
- Operation Invisible: A Tall Tail of the American Revolution
- Operation Jackpot
- Operation Kaukasus
- Operation Monarch
- Operation Moonlight
- Operation Napoleon
- Operation Orangutan
- Operation Sarajevo
- Operation Timepiece
- Operation Trickery
- Operation Underworld
- Operazione Cristopher
- Operação Tesouro
- Opere Complete di Italo Svevo (Italian Edition)
- Opetanie Mojzesza Karnowskiego
- Opettajatar
- Ophelia
- Ophelia's Muse
- Ophélie d'Arthur Rimbaud
- Opinions sociales
- Opium and the Romantic Imagination
- Opium Warfare
- OPO The Peace Monster
- Opplysningens stjerne Voltaire 1694-1778
- Opportunities: Jamie Leith in Darién
- Oppositions
- Opportunities: Jamie Leith in Darién
- Oppositions
- Oppression and Responsibility
- Opus Gemini I
- Opus Gemini II
- Opus Gemini III
- Opus Magnum
- Opération Dragon Rouge
- Opération ISKRA
- Or Even Eagle Flew
- Or I'll Dress You In Mourning
- Ora saremo liberi
- Oración
- Oracle Bone
- Oracle of the Reeds
- Oracles and Miracles and Zombies
- Oradour, le roman d'un procès
- ORAGE
- Oraiáphon
- Oral Sex Then and Now
- Orality and Performance in Classical Attic Prose
- Orality, Textuality, and the Homeric Epics
- Orange
- Orange and Green
- Orange Cerlo
- Orange Cerlo: One Day
- Orange County Punk
- Orangen und Datteln
- Orbital Velocity
- Orchidea császárné
- Orchidelirium: Book 1
- Orchis
- Ordeal of Richard Feverel — Complete