- American Republic, The, by O. A. Brownson
- Monsieur de Camors, by Octave Feuillet
- Stories of a Western Town, by Octave Thanet
- Waifs and Strays, etc, by O Henry
- Strictly Business, by O Henry
- Four Million, The, by O Henry
- Sixes and Sevens, by O Henry
- Cabbages and Kings, by O Henry
- Trimmed Lamp, et al, The, by O Henry
- Rolling Stones, by O. Henry
- Voice of the City, The, by O Henry
- Heart of the West, by O Henry
- Whirligigs, by O Henry
- Gift of the Magi, The, by O. Henry
- Options, by O. Henry
- Gentle Grafter, The, by O. Henry
- Roads of Destiny, by O. Henry
- Memoirs of General the Baron de Marbot Translated, The, by Oliver C. Colt
- Vicar of Wakefield, The, by Oliver Goldsmith
- She Stoops to Conquer, by Oliver Goldsmith
- Haste and Waste, by Oliver Optic
- Poor and Proud, by Oliver Optic
- Disturbances of the Heart, by Oliver T. Osborne
- Common Law, The, by Oliver Wendell Holmes Jr.
- Path of the Law, Oliver Wendell Holmes, The, by Oliver Wendell Holmes, Jr.
- Over the Teacups, by Oliver Wendell Holmes
- Our Hundred Days in Europe , by Oliver Wendell Holmes
- Autocrat of the Breakfast Table, The, by Oliver Wendell Holmes
- Autocrat of the Breakfast-Table, The, by Oliver Wendell Holmes, Sr.
- Memoir of John Lothrop Motley, The, by Oliver Wendell Holmes, Sr.
- Dream Life and Real Life, by Olive Schreiner
- Dreams, by Olive Schreiner
- Trooper Peter Halket of Mashonaland, by Olive Schreiner
- Woman and Labour, by Olive Schreiner
- Rubaiyat, by Omar Khayyam
- An Amiable Charlatan, by Oppenheim
- An Amiable Charlatan, by Oppenheim
- See America First, by Orville O. Hiestand
- Canadian Dominion, The, by Oscar D. Skelton
- Shorter Prose Pieces, by Oscar Wilde
- Picture of Dorian Gray, The, by Oscar Wilde
- Picture of Dorian Gray, The, by Oscar Wilde
- Ballad of Reading Gaol, The, by Oscar Wilde
- A Woman of No Importance, by Oscar Wilde
- Charmides and Other Poems, by Oscar Wilde
- Duchess of Padua, The, by Oscar Wilde
- De Profundis, by Oscar Wilde
- Happy Prince and Other Tales, The, by Oscar Wilde
- A House of Pomegranates, by Oscar Wilde
- An Ideal Husband, by Oscar Wilde
- Lord Arthur Savile's Crime and Other Stories, by Oscar Wilde
- Lady Windermere's Fan, by Oscar Wilde
- Intentions, by Oscar Wilde
- Poems, by Oscar Wilde
- Essays & Lectures, by Oscar Wilde
- Soul of Man, The, by Oscar Wilde
- Selected Poems of Oscar Wilde, by Oscar Wilde
- Importance of Being Earnest, The, by Oscar Wilde
- Salome, by Oscar Wilde
- Selected Prose of Oscar Wilde, by Oscar Wilde
- Oscar Wilde Miscellaneous, by Oscar Wilde
- Thrall of Leif the Lucky, The, by Ottilie A. Liljencrantz
- Santo Domingo, by Otto Schoenrich
- Santo Domingo, by Otto Schoenrich
- Under Two Flags, by Ouida [Louise de la Ramee]
- Short History of Wales, by Owen M. Edwards
- Cartrefi Cymru, by Owen M. Edwards
- Lucile, by Owen Meredith
- Philosophy 4 A Story of Harvard University, by Owen Wister
- Padre Ignacio, by Owen Wister
- Jimmyjohn Boss and Other Stories, The, by Owen Wister
- Lady Baltimore, by Owen Wister
- Lin McLean, by Owen Wister
- Mother, by Owen Wister
- A Straight Deal, by Owen Wister
- Virginian, The, by Owen Wister
- Path of the Law, The, by O. W. Holmes, Jr.
- Guardian Angel, The, by O. W. Holmes, Sr.
- A Mortal Antipathy, by O. W. Holmes, Sr.
- Elsie Venner, by O. W. Holmes, Sr.
- Medical Essays, by O. W. Holmes, Sr.