- The Seaboard Parish, CompleteAuthor: George MacDonaldReleased on Project Gutenberg: July 1, 2005
- The SearchAuthor: Grace Livingston HillReleased on Project Gutenberg: June 21, 2008
- The Search for the Silver City: A Tale of Adventure in YucatanAuthor: James OtisReleased on Project Gutenberg: May 2, 2007
- The Seats of the Mighty, CompleteAuthor: Gilbert ParkerReleased on Project Gutenberg: November 17, 2004
- The Seats of the Mighty, Volume 1Author: Gilbert ParkerReleased on Project Gutenberg: August 1, 2004
- The Seats of the Mighty, Volume 2Author: Gilbert ParkerReleased on Project Gutenberg: August 1, 2004
- The Seats of the Mighty, Volume 3Author: Gilbert ParkerReleased on Project Gutenberg: August 1, 2004
- The Seats of the Mighty, Volume 4Author: Gilbert ParkerReleased on Project Gutenberg: August 1, 2004
- The Seats of the Mighty, Volume 5Author: Gilbert ParkerReleased on Project Gutenberg: August 1, 2004
- The Second Battalion Royal Dublin Fusiliers in the South African War: With a Description of the Operations in the Aden HinterlandAuthor: Cecil Francis Romer, Arthur Edward MainwaringReleased on Project Gutenberg: May 26, 2008
- The Second Book of Modern Verse: A Selection from the Work of Contemporaneous American PoetsAuthor: Jessie Belle RittenhouseReleased on Project Gutenberg: January 1, 1998
- The Second ChanceAuthor: Nellie L. McClungReleased on Project Gutenberg: July 15, 2007
- The Second Class Passenger: Fifteen StoriesAuthor: Perceval GibbonReleased on Project Gutenberg: March 6, 2006
- The Second DelugeAuthor: Garrett Putman ServissReleased on Project Gutenberg: October 1, 2005
- The Second Funeral of NapoleonAuthor: William Makepeace ThackerayReleased on Project Gutenberg: May 22, 2006
- The Second GenerationAuthor: David Graham PhillipsReleased on Project Gutenberg: March 1, 2004
- The Second HoneymoonAuthor: Ruby M. (Ruby Mildred) AyresReleased on Project Gutenberg: January 2, 2006
- The Second Jungle BookAuthor: Rudyard KiplingReleased on Project Gutenberg: October 1, 1999
- The Second LatchkeyAuthor: C. N. (Charles Norris) Williamson, A. M. (Alice Muriel) WilliamsonReleased on Project Gutenberg: May 29, 2006
- The Second Story of Meno: A Continuation of Socrates' Dialogue with Meno in Which the Boy Proves Root 2 is IrrationalAuthor: UnknownReleased on Project Gutenberg: July 9, 2008
- The Second Thoughts of an Idle FellowAuthor: Jerome K. (Jerome Klapka) JeromeReleased on Project Gutenberg: October 1, 1999
- The Second ViolinAuthor: Grace S. (Grace Smith) RichmondReleased on Project Gutenberg: August 17, 2004
- The second William PennAuthor: W. H. (William Henry) RyusReleased on Project Gutenberg: February 1, 2006
- The Second-Story ManAuthor: Upton SinclairReleased on Project Gutenberg: July 1, 2002
- The Secret AdversaryAuthor: Agatha ChristieReleased on Project Gutenberg: January 1, 1998
- The Secret Agent: A Simple TaleAuthor: Joseph ConradReleased on Project Gutenberg: July 1, 1997
- The Secret Chamber at ChadAuthor: Evelyn Everett-GreenReleased on Project Gutenberg: April 20, 2005
- The Secret CityAuthor: Hugh WalpoleReleased on Project Gutenberg: May 1, 2004
- The Secret GardenAuthor: Frances Hodgson BurnettReleased on Project Gutenberg: March 1, 1994
- The Secret GardenAuthor: Frances Hodgson BurnettReleased on Project Gutenberg: December 26, 2005
- The Secret Guide to ComputersAuthor: Russ WalterReleased on Project Gutenberg: September 1, 1996
- The Secret History of the Court of JustinianAuthor: ProcopiusReleased on Project Gutenberg: July 16, 2004
- The Secret Memoirs of the Courts of Europe: William II, Germany; Francis Joseph, Austria-Hungary, Volume I. (of 2)Author: Fontenoy, marquise deReleased on Project Gutenberg: June 1, 2004
- The Secret of a Happy Home (1896)Author: Marion HarlandReleased on Project Gutenberg: October 4, 2005
- The Secret of Divine CivilizationAuthor: ʻAbdu'l-BaháReleased on Project Gutenberg: September 12, 2006
- The Secret of DreamsAuthor: Yacki RaizizunReleased on Project Gutenberg: August 8, 2004
- The Secret of the CreationAuthor: Pollyen, Howard D.Released on Project Gutenberg: May 25, 2007
- The secret of the islandAuthor: Jules Verne, Agnes Kinloch KingstonReleased on Project Gutenberg: May 16, 2007
- The Secret of the NightAuthor: Gaston LerouxReleased on Project Gutenberg: March 1, 1999
- The Secret of the Storm CountryAuthor: Grace Miller White, Lucius Wolcott HitchcockReleased on Project Gutenberg: February 8, 2007
- The Secret of the TowerAuthor: Anthony HopeReleased on Project Gutenberg: November 1, 2003
- The Secret PassageAuthor: Fergus HumeReleased on Project Gutenberg: October 1, 2003
- The Secret Places of the HeartAuthor: H. G. (Herbert George) WellsReleased on Project Gutenberg: February 22, 2006
- The Secret PowerAuthor: Marie CorelliReleased on Project Gutenberg: March 1, 2003
- The Secret RoseAuthor: W. B. (William Butler) YeatsReleased on Project Gutenberg: May 1, 2004
- The Secret SharerAuthor: Joseph ConradReleased on Project Gutenberg: January 9, 2006
- The Secret Wireless; Or, The Spy Hunt of the Camp Brady PatrolAuthor: Lewis E. (Lewis Edwin) Theiss, Frank T. MerrillReleased on Project Gutenberg: June 28, 2007
- The Secret WitnessAuthor: George GibbsReleased on Project Gutenberg: June 3, 2008
- The Secrets of the German War OfficeAuthor: Graves, Armgaard Karl, Edward Lyell FoxReleased on Project Gutenberg: November 1, 2004
- The Secrets of the Great City: A Work Descriptive of the Virtues and the Vices, the Mysteries, Miseries and Crimes of New York CityAuthor: James Dabney McCabeReleased on Project Gutenberg: September 1, 2005
- The Secrets of the Princesse de CadignanAuthor: Honoré de Balzac, Katharine Prescott WormeleyReleased on Project Gutenberg: August 31, 2005
- The Seed of the Toc-Toc BirdsAuthor: George Henry WeissReleased on Project Gutenberg: December 12, 2007
- The SeekerAuthor: Harry Leon Wilson, Rose Cecil O'NeillReleased on Project Gutenberg: May 8, 2005
- The Seigneurs of Old Canada : A Chronicle of New World FeudalismAuthor: William Bennett Munro, H. H. (Hugh Hornby) Langton, George McKinnon WrongReleased on Project Gutenberg: November 1, 2003
- The Seminole Indians of Florida: Fifth Annual Report of the Bureau of Ethnology to the Secretary of the Smithsonian Institution, 1883-84, Government Printing Office, Washington, 1887, pages 469-532Author: Clay MacCauleyReleased on Project Gutenberg: September 1, 2006
- The SentimentalistsAuthor: George MeredithReleased on Project Gutenberg: September 1, 2003
- The Sequel of Appomattox: A Chronicle of the Reunion of the StatesAuthor: Walter L. (Walter Lynwood) FlemingReleased on Project Gutenberg: November 1, 2001
- The Servant in the HouseAuthor: Charles Rann KennedyReleased on Project Gutenberg: April 1, 2004
- The Servant ProblemAuthor: Robert F. YoungReleased on Project Gutenberg: October 29, 2007
- The Settler and the SavageAuthor: R. M. (Robert Michael) BallantyneReleased on Project Gutenberg: June 6, 2007