- Open If You Dare
- Open Your Mind
- Open: A Toolkit for How Magic and Messed Up Life Can Be
- Openly Straight
- Openly, Honestly
- Operatic
- Operation Frog Effect
- Operation Josh Taylor
- Operation Pucker Up
- Operation Stay in England
- Operation Tiger
- POR DENTRO DA OPERAÇÃO PALMARES
- Ophelia and the Marvelous Boy
- Opowieści o uczuciach
- Opposite Island
- Oracle
- Oracles of Delphi Keep
- Orchestra in Our Brain
- Order of the Majestic
- Orphan Island
- Orphan Train Girl
- Orphaned (Ape Quartet #4)
- Os miseráveis
- Oscar Season
- Other Boys
- Other Words for Home
- Other Worlds
- Othergirl
- Otherwise Known as Sheila the Great
- Otis Grows
- OTOLI
- Our Chemical Hearts
- Our Friendship Rules
- Our New World
- Our Song
- Our Stories, Our Voices
- Our Teacher Is a Vampire and Other (Not) True Stories
- Out of Darkness
- Out of My Heart
- Out of My Mind
- Out of My Shell
- Out of Place
- Out of Reach
- Out of Shadows
- Out of the Ashes
- Out of the Blue
- Out of the Box
- Out of The Easy
- Out of Tune
- Out Walked Mel
- Outcast
- Outcasts United
- Outrageously Alice
- Outside Beauty
- Outside In
- Over & Out #10
- Over the Moon
- Overcoming Anorexia Nervosa 2nd Edition
- Overcoming My Mother's Addictions
- Overcoming The Storms Of Life
- Overload
- Overnight
- Overturned
- Overworld in Flames
- Ovily Pumpkin
- Own Your Period
- Ozzie, the Courageous Otter
- Où es-tu Yazid ?
- Où est Agota?