| Oedipus at Colonus | Sophocles, | "Drama"
| 56 | 425 BC | 5 | 1994-09-02 |
| Oedipus Rex | Sophocles, | "Drama"
| 68 | 425 BC | 6 | 1994-09-02 |
| Of a Feather | Weidensaul, Scott | "Nature/Science"
| 314 | 2007 | 6 | 2023-02-01 |
| Of Human Bondage | Maugham, W. Somerset | "Fiction - General"
| 607 | 1915 | 5 | 1999-04-11 |
| Of Mice and Men | Steinbeck, John | "Fiction - General"
| 118 | 1937 | 5 | 1989-04-20 |
| Of Plymouth Plantation | Bradford, William | "U.S. History - Cultural"
| 471 | 1650 | 7 | 2003-02-17 |
| Of Prairie, Woods, and Water | Greenberg (ed.), Joel | "Nature/Science"
| 402 | 2008 | 5 | 2025-10-08 |
| Off for the Sweet Hereafter | Pearson, T.R. | "Fiction - Adventure"
| 283 | 1986 | 5 | 2016-05-16 |
| Off the Map | Nelson, Derek | "Travel"
| 186 | 1997 | 6 | 2000-04-04 |
| Official Guide to Colonial Williamsburg | Olmert, Michael | "Travel"
| 154 | 1985 | 5 | 1995-06-11 |
| Oh! To Be in England (4) | Bates, H.E. | "Fiction - Humorous Novels"
| 101 | 1963 | 6 | 2019-06-02 |
| Oh, the Places You'll Go | Seuss, Dr. | "Picture Book"
| 44 | 1990 | 4 | 1998-07-26 |
| Old Bones the Wonder Horse | Pace, Mildred Mastin | "Fiction - Chapter Books"
| 95 | 1955 | 6 | |
| Old Curiosity Shop, The | Dickens, Charles | "Fiction - General"
| 680 | 1841 | 7 | 1998-11-14 |
| Old Farm, The | Mellick, Jr., Andrew | "Nature/Science"
| 203 | | 5 | 1988-08-05 |
| Old Fort Williams | Black, Arthur | "World History - Military"
| 69 | 1985 | 7 | 1996-07-06 |
| Old Forts of the Great Lakes | Barry, James P. | "U.S. History - Military"
| 155 | 1994 | 7 | 1996-07-11 |
| Old Glory | Raban, Jonathan | "Travel"
| 409 | 1981 | 7 | 2013-11-26 |
| Old Hickory | Davis, Burke | "U.S. History - Political"
| 386 | | 7 | 1989-05-15 |
| Old London Bridge | Pierce, Patricia | "World History - Cultural"
| 295 | 2001 | 6 | 2003-06-17 |
| Old Man and the Sea, The | Hemingway, Ernest | "Fiction - Adventure"
| 127 | 1952 | 8 | 1996-01-27 |
| Old Possum's Book of Practical Cats | Eliot, T.S. | "Poetry Collections"
| 24 | 1939 | 7 | 1994-04-08 |
| Old Reliable, The | Wodehouse, P.G. | "Fiction - Humorous Novels"
| 123 | 1951 | 6 | 2021-02-27 |
| Old Times on the Upper Mississippi | Merrick, George Byron | "Travel"
| 305 | 1909 | 8 | 1997-02-15 |
| Old Tippecanoe | Cleaves, Freeman | "U.S. History - Political"
| 343 | 1939 | 8 | 1989-09-20 |
| Old Ways, The | Macfarlane, Robert | "Travel"
| 448 | | 6 | 2013-06-22 |
| Old Yeller | Gipson, Fred | "Fiction - Chapter Books"
| 117 | 1956 | 5 | 1997-05-12 |
| Oliver Twist | Dickens, Charles | "Fiction - General"
| 494 | 1838 | 6 | 1989-05-04 |
| Olura | Household, Geoffrey | "Fiction - Mystery"
| 224 | 1965 | 5 | 2022-10-10 |
| Omega-Minus | Allbeury, Ted | "Fiction - Adventure"
| 181 | 1976 | 7 | 1993-01-03 |
| On a Slow Train Through Arkansaw | Jackson, Thomas William | "Humor"
| 96 | 1903 | 5 | 2023-07-26 |
| On Beyond Zebra! | Seuss, Dr. | "Picture Book"
| 48 | 1955 | 7 | 1997-08-30 |
| On Desperate Ground | Sides, Hampton | "U.S. History - Military"
| 337 | 2018 | 8 | 2021-08-27 |
| On Her Majesty's Secret Service | Fleming, Ian | "Fiction - Adventure"
| 190 | 1963 | 8 | 1989-02-24 |
| On Jungle Trails | Buck, Frank | "Travel"
| 280 | 1936 | 5 | 2004-05-08 |
| On Kingdom Mountain | Mosher, Howard Frank | "Fiction - Adventure"
| 357 | 2014 | 6 | 2023-09-13 |
| On the Banks of Plum Creek | Wilder, Laura Ingalls | "Fiction - General"
| 339 | 1937 | 7 | 2002-10-13 |
| On the Beach | Shute, Nevil | "Fiction - Adventure"
| 234 | 1957 | 8 | 1987-08-06 |
| On the Island | Graves, Tracey Garvis | "Fiction - Adventure"
| 319 | 2012 | 5 | 2025-09-14 |
| On the Road | Kerouac, Jack | "Fiction - General"
| 310 | 1957 | 2 | 1993-01-23 |
| On the Run | MacDonald, John D. | "Fiction - Mystery"
| 224 | 1963 | 5 | 2015-07-22 |
| On the Water | Stone, Nathaniel | "Travel"
| 317 | 2002 | 7 | 2013-11-30 |
| On the Wing | Tennant, Alan | "Nature/Science"
| 301 | 2004 | 7 | 2005-03-12 |
| On War | Clausewitz, Carl von | "Philosophy"
| 310 | 1832 | 6 | 1995-11-05 |
| On Writing Well | Zinsser, William | "Literature/Essays"
| 294 | 1976 | 7 | 2002-02-27 |
| Once and Future King, The | White, T.H. | "Fiction - S. F./Fantasy"
| 639 | 1958 | 7 | 1998-04-20 |
| Once More Around the Park | Angell, Roger | "Sports"
| 351 | 1991 | 8 | 2022-12-18 |
| Once Upon a Telephone | Stern, Emily Gwathmey and Ellen | "Reference/Miscellaneous"
| 133 | 1994 | 5 | 2001-01-19 |
| One Corpse Too Many | Peters, Ellis | "Fiction - Mystery"
| 192 | 1979 | 8 | 1997-10-18 |
| One Day in the Life of Ivan Denisovich | Solzhenitsyn, Alexander | "Fiction - General"
| 158 | 1962 | 7 | 1994-11-20 |
