Books about Man-woman relationships -- Fiction (sorted alphabetically)
- Numa Roumestan: Moeurs Parisiennes (French) Alphonse Daudet
- Nuoruuden rakkautta (Finnish) Frank Norris
- Object: matrimony Montague Glass
- Old Adam: A Story of Adventure Arnold Bennett
- Old Crow Alice Brown
- Old-Dad Eleanor Hallowell Abbott
- Old Maids' Club Israel Zangwill
- Old Mole Gilbert Cannan
- Old Rose and Silver Myrtle Reed
- Omenapuu (Finnish) John Galsworthy
- One Day At Arle Frances Hodgson Burnett
- Only an Incident Grace Denio Litchfield
- Orchard of Tears Sax Rohmer
- Orchid Robert Grant
- Orphan Dinah Eden Phillpotts
- Our Elizabeth: A Humour Novel Florence A. Kilpatrick
- Our Mr. Wrenn: The Romantic Adventures of a Gentle Man Sinclair Lewis
- Out of the blue Bertrand W. Sinclair
- Out of the sea Leigh Brackett
- Out of the Woods Elisabeth Sanxay Holding
- Overlooked Maurice Baring
- Pandora Henry James
- Paradise Garden: The Satirical Narrative of a Great Experiment George Gibbs
- Paris (French) Émile Zola
- Passing By Maurice Baring