- American revolution, a nonfiction companion to Revolutionary War on Wednesday, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Dolphins and sharks, a nonfiction companion to Magic tree house #9 : Dolphins at daybreak, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Dogsledding and extreme sports, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Carlo Molinari
- Horse heroes, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Horse heroes, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Ghosts, "A nonfiction companion to Magic Tree House #42: A Good Night for Ghosts.", by Natalie Pope Boyce ; illustrated by Sal Murdocca
- Leprechauns and Irish folklore, by Mary Pope Osborne and Natalie Pope Boyce
- Dog heroes, a nonfiction companion to Dogs in the dead of night, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Sabertooths and the ice age, a nonfiction companion to Magic tree house #7: Sunset of the sabertooth, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Magic tricks from the tree house, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Leonardo da Vinci, a nonfiction companion to Magic tree house #38: Monday with a mad genius, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Rags and riches, kids in the time of Charles Dickens, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Sabertooths and the Ice Age, a nonfiction companion to Sunset of the sabertooth, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Polar bears and the Arctic, a nonfiction companion to Polar bears past bedtime, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Wild West, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Isidre Monés
- Tsunamis and other natural disasters, a nonfiction companion to magic tree house #28, High tide in Hawaii, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Incredible fact book, Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Soccer, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Leonardo da Vinci, a nonfiction companion to Monday with a mad genius, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Magic tree house survival guide, Mary Pope Osborne and Natalie Pope Boyce
- Pandas and other endangered species, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Tsunamis and other natural disasters, a nonfiction companion to High tide in Hawaii, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Sea monsters, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Warriors, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Isidre Monés
- Heroes for all times, a nonfiction companion to Magic tree house #51: high time for heroes, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Baseball, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Carlo Molinari
- Dolphins and sharks, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Abraham Lincoln, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Survival guide, Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- The Random House book of Bible stories, retold by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Michael Welply
- Pilgrims, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Benjamin Franklin, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Isidre Monés
- Dog heroes, a nonfiction companion to Magic tree house #46: Dogs in the dead of night, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Polar bears and the Arctic, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Ancient Greece and the Olympics, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Dragons and mythical creatures, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Carlo Molinari
- Snakes and other reptiles, a nonfiction companion to Magic tree house #45: A crazy day with cobras, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Penguins and Antarctica, a nonfiction companion to Eve of the emperor penguins, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Vikings, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Carlo Molinari
- Leprechauns and Irish folklore, a nonfiction companion to Leprechaun in late Winter, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Pandas and other endangered species, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Ninjas and samurai, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Ancient Greece and the Olympics, a nonfiction companion to Hour of the Olympics, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Narwhals and other whales, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Isidre Monés
- Snakes and other reptiles, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Heroes for all times, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Sea monsters, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Penguins and Antarctica, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Ancient Rome and Pompeii, a nonfiction companion to Vacation under the volcano, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Sal Murdocca
- Llamas and the Andes, by Mary Pope Osborne and Natalie Pope Boyce ; illustrated by Isidre Monés