Ocean Girl– Jane Buehler
October Light– John Gardner
Octopus and the Orangutan, The– Eugene Linden
Octopus Scientists, The– Sy Montgomery
Of Parrots and People– Mira Tweti
Of Wolves and Men– Barry Lopez
Old Country, The– Mordicai Gerstein
Old Crow– Sharon Mackay
Old Mother West Wind– Thornton Burgess
Old Ramon– Jack Schaefer
Old School– Tobias Wolff
Old Yeller – Fred Gipson
Oldest Living Things in the World, The– Rachel Sussman
Olive’s Ocean– Kevin Henkes
Omnivore’s Dilemma, The – Michael Pollan
On the Far Side of the Mountain– Jean Craighead George
On the Move– Oliver Sacks
On the Wing– Alan Tennant
Once Upon an Eskimo Time– Edna Wilder
Once Upon a Flock– Lauren Scheuer
One Child – Torey Hayden
One Day at Teton Marsh – Sally Carrighar
One Day on Beetle Rock – Sally Carrighar
One-Eyed Cat– Paula Fox
One Good Horse– Tom Groneberg
One-Hour Garden, The – Joanna Smith
One Small Boat – Kathy Harrison
One Thousand Chestnut Trees– Mira Stout
One Thousand White Women– Jim Fergus
One Trick Pony– Nathan Hale
One Wild Bird at a Time– Bernd Heinrich
Only Alien on the Planet, The – Kristen Randle
Only Girl in the World, The– Maude Julien
Onward and Upward in the Garden– Katharine White
Oogy– Larry Levin
Onions in the Stew– Betty Macdonald
Operating Instructions– Anne Lamott
Ordinary Love and Good Will– Jane Smiley
Ordinary People– Judith Guest
Ordinary Princess, The – M.M. Kaye
Ordinary Wolves – Seth Kantner
Organized Enough– Amanda Sullivan
Origin, The– Irving Stone
Orphan– Faith McNulty
Oryx and Crake– Margaret Atwood
Other, The (Animorphs #40) – K.A. Applegate
Other End of the Leash, The– Patricia McConnell
Other Lives – Andre Brink
Other Wind, The– Ursula K. LeGuin
Otherwise Normal People– Aurelia C. Scott
Our Horses in Egypt– Rosalind Belben
Our House in Arusha– Sara Tucker
Our Native Fishes– John R. Quinn
Our Precarious Habitat– Melvin Benarde
Out in the Midday Sun– Elspeth Huxley
Out of Harm’s Way– Terri Crisp
Out of My Mind– Sharon Draper
Out of Noah’s Ark– Herbert Wendt
Out Stealing Horses– Per Petterson
Overloaded Ark, The– Gerald Durrell
Owen and Mzee– Craig Hatkoff, et al
Owl: A Year in the Lives– Paul Bannick
Owl – William Service
Owls Aren’t Wise and Bats Aren’t Blind – Warner Shedd
Owl Service, The– Alan Garner