| Omnibuses and cabs
Henry Charles Moore | |
| Omnilingual
H. Beam Piper | |
| Omoo: Adventures in the South Seas
Herman Melville | |
| Omphalos: An Attempt to Untie the Geological Knot
Philip Henry Gosse | |
| On
Hilaire Belloc | |
| On a Chinese Screen
W. Somerset Maugham | |
| On a Donkey's Hurricane Deck / A Tempestous Voyage of Four Thousand and Ninety-Six Miles Across the American Continent on a Burro, in 340 Days and 2 Hours, Starting Without a Dollar and Earning My Way
R. Pitcher Woodward | |
| On a Dynamical Top, for exhibiting the phenomena of the motion of a system of invariable form about a fixed point, with some suggestions as to the Earth's motion
James Clerk Maxwell | |
| On a lark to the planets / A sequel to "The wonderful electric elephant"
Frances Trego Montgomery | |
| On a Torn-Away World; Or, the Captives of the Great Earthquake
Roy Rockwood |
