Origin of Species
Robert F. Young
The Orb of Probability
Nat Schachner
The Orangery
K. D. Wentworth
Oracles
Robert Reed
The Oracle and the Mountains
Stephen King
Roland (1)
Or Battle's Sound
Harry Harrison
Matter Transmitter (1)
Options
John Varley
Eight Worlds (1)
The Operator
Christopher Anvil
Federation of Humanity (1)
Operation Syndrome
Frank Herbert
Operation High Time
Jacqueline Lichtenberg
Sime/Gen (13)
Operation Haystack
Operation Desert Fox
Mercedes Lackey & Larry Dixon
Bolo (1)
Operation Afreet
Poul Anderson
Operation Chaos (1)
Ooze
Anthony M. Rud
Oomphel in the Sky
H. Beam Piper
Federation (1)
Only the Dead Know Jokertown
John J. Miller
Wild Cards (1)