| Robert C. O'Brien |
Mrs. Frisby and the Rats of NIMH (age 9-12) adventure , brilliant protagonist |
| Barbara O'Connor |
How to Steal a Dog (age 8-11) growing up , family , enterprise |
| Kathleen O'Dell |
Agnes Parker, Girl in Progress (age 9-12) in: Agnes Parker Series growing up , friendship , school |
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Agnes Parker, Happy Camper? (age 9-12) in: Agnes Parker Series growing up , friendship , school | |
| Scott O'Dell |
Sing Down the Moon (age 9-12) adventure , historical |
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Zia (age 9-12) adventure , historical | |
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Sarah Bishop (age 10+) war , survival , family , historical | |
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Island of the Blue Dolphins (age 9-12) survival , adventure , historical | |
| Barbara Oconnor |
The Small Adventure of Popeye and Elvis (age 8-11) realistic , self-reliance , adventure , humor |
| Kenneth Oppel |
Silverwing (age 9-12) in: The Silverwing Trilogy growing up , action , adventure |
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Sunwing (age 9-12) in: The Silverwing Trilogy growing up , action , adventure | |
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Firewing (age 9-12) in: The Silverwing Trilogy growing up , action , adventure | |
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Darkwing (age 10+) fantasy , action , adventure | |
| Uri Orlev |
The Island on Bird Street (age 9-12) war , survival , historical |
| Wendy Orr |
Mokie and Bik (age 7-10) humor , family |
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Lost! a Dog Called Bear (age 8-11) in: Rainbow Street Shelter Series realistic , adventure , animals | |
| Mary Pope Osborne |
Afternoon on the Amazon (age 7-10) in: Magic Tree House Series adventure , historical |
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Blizzard of the Blue Moon (age 7-10) in: Magic Tree House Series adventure , historical | |
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Buffalo Before Breakfast (age 7-10) in: Magic Tree House Series adventure , historical | |
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Christmas in Camelot (age 7-10) in: Magic Tree House Series adventure , historical | |
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Civil War on Sunday (age 7-10) in: Magic Tree House Series adventure , historical | |
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A Crazy Day with Cobras (age 7-10) in: Magic Tree House Series adventure , historical | |
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Dark Day in the Deep Sea (age 7-10) in: Magic Tree House Series adventure , historical | |
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Day of the Dragon King (age 7-10) in: Magic Tree House Series adventure , historical | |
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Dingoes at Dinnertime (age 7-10) in: Magic Tree House Series adventure , historical | |
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Dinosaurs Before Dark (age 7-10) in: Magic Tree House Series adventure , historical | |
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Dogs in the Dead of Night (age 7-10) in: Magic Tree House Series adventure , historical | |
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Dolphins at Daybreak (age 7-10) in: Magic Tree House Series adventure , historical | |
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Dragon of the Red Dawn (age 7-10) in: Magic Tree House Series adventure , historical | |
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Earthquake in the Early Morning (age 7-10) in: Magic Tree House Series adventure , historical | |
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Eve of the Emperor Penguin (age 7-10) in: Magic Tree House Series adventure , historical | |
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A Ghost Tale for Christmas Time (age 7-10) in: Magic Tree House Series adventure , historical | |
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Ghost Town at Sundown (age 7-10) in: Magic Tree House Series adventure , historical | |
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Good Morning, Gorillas (age 7-10) in: Magic Tree House Series adventure , historical | |
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A Good Night for Ghosts (age 7-10) in: Magic Tree House Series adventure , historical | |
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Haunted Castle on Hallows Eve (age 7-10) in: Magic Tree House Series adventure , historical | |
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Hour of the Olympics (age 7-10) in: Magic Tree House Series adventure , historical | |
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The Knight at Dawn (age 7-10) in: Magic Tree House Series adventure , historical | |
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Leprechaun in Late Winter (age 7-10) in: Magic Tree House Series adventure , historical | |
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Lions at Lunchtime (age 7-10) in: Magic Tree House Series adventure , historical | |
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Midnight on the Moon (age 7-10) in: Magic Tree House Series adventure , historical | |
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Monday With a Mad Genius (age 7-10) in: Magic Tree House Series adventure , historical | |
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Moonlight on the Magic Flute (age 7-10) in: Magic Tree House Series adventure , historical | |
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Mummies in the Morning (age 7-10) in: Magic Tree House Series adventure , historical | |
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Night of the New Magicians (age 7-10) in: Magic Tree House Series adventure , historical | |
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Night of the Ninjas (age 7-10) in: Magic Tree House Series adventure , historical | |
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Pirates Past Noon (age 7-10) in: Magic Tree House Series adventure , historical | |
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Polar Bears Past Bedtime (age 7-10) in: Magic Tree House Series adventure , historical | |
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Revolutionary War on Wednesday (age 7-10) in: Magic Tree House Series adventure , historical | |
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Season of the Sandstorms (age 7-10) in: Magic Tree House Series adventure , historical | |
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Stage Fright on a Summer Night (age 7-10) in: Magic Tree House Series adventure , historical | |
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Summer of the Sea Serpent (age 7-10) in: Magic Tree House Series adventure , historical | |
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Sunset of the Sabertooth (age 7-10) in: Magic Tree House Series adventure , historical | |
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Thanksgiving on Thursday (age 7-10) in: Magic Tree House Series adventure , historical | |
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Tigers at Twilight (age 7-10) in: Magic Tree House Series adventure , historical | |
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Tonight on the Titanic (age 7-10) in: Magic Tree House Series adventure , historical | |
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Twister on Tuesday (age 7-10) in: Magic Tree House Series adventure , historical | |
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Vacation Under the Volcano (age 7-10) in: Magic Tree House Series adventure , historical | |
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Viking Ships at Sunrise (age 7-10) in: Magic Tree House Series adventure , historical | |
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Winter of the Ice Wizard (age 7-10) in: Magic Tree House Series adventure , historical | |
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My Secret War: the World War II Diary of Madeline Beck, Long Island, New York, 1941 (age 8-11) in: Dear America Series war , identity , letters/journal , historical | |
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Standing in the Light: the Captive Diary of Catherine Carey Logan, Delaware Valley, Pennsylvania, 1763 (age 8-11) in: Dear America Series war , identity , letters/journal , historical | |
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My Brother's Keeper: Virginia's Civil War Diary (age 7-10) in: My America Series letters/journal , historical |