- Notes to Shakespeare, Volume III: The TragediesAuthor: Samuel Johnson, Arthur SherboReleased on Project Gutenberg: April 6, 2005
- Notes to the Complete Poetical Works of Percy Bysshe ShelleyAuthor: Mary Wollstonecraft ShelleyReleased on Project Gutenberg: November 1, 2003
- Noteworthy families (modern science)Author: Francis Galton, Edgar SchusterReleased on Project Gutenberg: November 21, 2005
- Nothing to EatAuthor: Alger, Horatio, Jr., Thomas Chandler HaliburtonReleased on Project Gutenberg: June 1, 2004
- Noto: An Unexplored Corner of JapanAuthor: Percival LowellReleased on Project Gutenberg: April 1, 2001
- Notre-Dame de ParisAuthor: Victor Hugo, Isabel Florence HapgoodReleased on Project Gutenberg: April 1, 2001
- Noughts and Crosses: Stories, Studies and SketchesAuthor: Arthur Quiller-CouchReleased on Project Gutenberg: May 19, 2005
- Novel NotesAuthor: Jerome K. (Jerome Klapka) JeromeReleased on Project Gutenberg: January 1, 2000
- Novelas CortasAuthor: Pedro Antonio de Alarcón, William F. (William Frederic) GieseReleased on Project Gutenberg: April 4, 2005
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- Number SeventeenAuthor: Louis TracyReleased on Project Gutenberg: January 1, 2004
- Nuttie's FatherAuthor: Charlotte M. (Charlotte Mary) YongeReleased on Project Gutenberg: May 1, 2003
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- O+FAuthor: Wetterau, John MoncureReleased on Project Gutenberg: February 1, 2004
- O. Henry Memorial Award Prize Stories of 1919Author: Society of Arts and Sciences (U.S.) [Editor], Blanche Colton WilliamsReleased on Project Gutenberg: April 1, 2004
- O. Henry Memorial Award Prize Stories of 1920Author: Society of Arts and Sciences (U.S.) [Editor], Blanche Colton WilliamsReleased on Project Gutenberg: March 1, 2004
- O. Henry Memorial Award Prize Stories of 1921Author: Society of Arts and Sciences (U.S.) [Editor], Blanche Colton Williams, Elizabeth (Elizabeth Alexander Heermann) Alexander, Maryland Allen, Thomas BeerReleased on Project Gutenberg: March 1, 2004
- O. T., A Danish RomanceAuthor: H. C. (Hans Christian) AndersenReleased on Project Gutenberg: February 1, 2005
- Oak OpeningsAuthor: James Fenimore CooperReleased on Project Gutenberg: July 1, 2003
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- Oberheim (Voices): A Chronicle of WarAuthor: Leadem, ChristopherReleased on Project Gutenberg: October 23, 2004
- Obiter DictaAuthor: Augustine BirrellReleased on Project Gutenberg: January 1, 2005
- Obiter Dicta: Second SeriesAuthor: Augustine BirrellReleased on Project Gutenberg: June 10, 2007
- Object Lessons on the Human Body: A Transcript of Lessons Given in the Primary Department of School No. 49, New York CityAuthor: Sarah F. (Sarah Frances) Buckelew, Margaret W. (Margaret Wiseham) LewisReleased on Project Gutenberg: March 21, 2005
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- Observations By Mr. DooleyAuthor: Finley Peter DunneReleased on Project Gutenberg: December 1, 2003
- Observations of a Retired VeteranAuthor: Henry C. TinsleyReleased on Project Gutenberg: October 1, 2004
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- Observations on the Effects of the Corn Laws, and of a Rise or Fall in the Price of Corn on the Agriculture and General Wealth of the CountryAuthor: T. R. (Thomas Robert) MalthusReleased on Project Gutenberg: August 1, 2003
- Observations on the Mussulmauns of India: Descriptive of Their Manners, Customs, Habits and Religious Opinions Made During a Twelve Years' Residence in Their Immediate SocietyAuthor: Meer Hasan Ali, Mrs., William CrookeReleased on Project Gutenberg: August 7, 2004
- Observations upon the Prophecies of Daniel, and the Apocalypse of St. JohnAuthor: Isaac NewtonReleased on Project Gutenberg: October 15, 2005
- Observations Upon the Windward Coast of Africa: The religion, character, customs, &c. of the natives; with a system upon which they may be civilized, and a knowledge attained of the interior of this extraordinary quarter of the globe; and upon the natural and commercial resources of the country; madAuthor: Corry, JosephReleased on Project Gutenberg: June 1, 2004
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- Occasional Poems: Part 3 from Volume IV of The Works of John Greenleaf WhittierAuthor: John Greenleaf WhittierReleased on Project Gutenberg: December 1, 2005
- Occasional Thoughts in Reference to a Vertuous or Christian lifeAuthor: Masham, Damaris, LadyReleased on Project Gutenberg: August 25, 2004
- Occult Chemistry: Clairvoyant Observations on the Chemical ElementsAuthor: Annie Besant, C. W. (Charles Webster) Leadbeater, A. P. (Alfred Percy) SinnettReleased on Project Gutenberg: June 14, 2005
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- October VagabondsAuthor: Richard Le GallienneReleased on Project Gutenberg: December 1, 2003
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- Odd Charges: Odd Craft, Part 13.Author: W. W. (William Wymark) Jacobs, Will OwenReleased on Project Gutenberg: April 1, 2004
- Odd craft [complete]Author: W. W. (William Wymark) Jacobs, Will OwenReleased on Project Gutenberg: April 1, 2004
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- Oddsfish!Author: Robert Hugh BensonReleased on Project Gutenberg: July 13, 2005
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- Of Human BondageAuthor: W. Somerset (William Somerset) MaughamReleased on Project Gutenberg: October 1, 1995
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- Officer and Man: 1901Author: Louis BeckeReleased on Project Gutenberg: April 12, 2008
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