The Magic Tree House series, written by Mary Pope Osborne and published by Random House, chronicles the adventures of Jack & Annie as they travel to distance places or go back in time.

The original series is made up of 37 books for young children. An additional 12 books that build off the original series is called the Merlin Mission series.

The author, along with her husband and sister, also write a companion non-fiction series called The Magic Tree House Research Guides consisting of 18 books. Each Guide is related to one of the books in the original series.

They can often be found at garage sales, book sales, and thrift stores for $.50 each or less.

Complete, or near complete, runs of the series will normally bring between $1.50 and $2.50 per book. When the Research Guides are included that figure can, at times, increase to $3 to $5 for each book.

With smaller lots of 10 to 15 books it’s probably more realistic to expect $1 to $2 for each book in the lot. Still a nice profit if you have only paid $.25 or less.

The titles in the original series are:

• Dinosaurs Before Dark
• The Knight At Dawn
• Mummies In The Morning
• Pirates Past Noon
• Night Of The Ninjas
• Afternoon On The Amazon
• Sunset Of The Sabertooth
• Midnight On The Moon
• Dolphins At Daybreak
• Ghost Town At Sundown
• Lions At Lunchtime
• Polar Bears Past Bedtime
• Vacation Under The Volcano
• Day Of The Dragon King
• Viking Ships At Sunrise
• Hour Of The Olympics
• Tonight On The Titanic
• Buffalo Before Breakfast
• Tigers At Twilight
• Dingoes At Dinnertime
• Civil War On Sunday
• Revolutionary War On Wednesday
• Twister On Tuesday
• Thanksgiving On Thursday
• High Tide In Hawaii

The Merlin Mission series contains the following titles:

• Christmas In Camelot
• Haunted Castle On Hallows Eve
• Summer Of The Sea Serpent
• Winter Of The Ice Wizard
• Carnival At Candlelight
• Season Of The Sandstorms
• Night Of The New Magicians
• Blizzard Of The Blue Moon
• Dragon Of The Red Dawn
• Monday With A Mad Genius
• Dark Day In The Deep Sea
• Eve Of The Emperor Penguin

The eighteen Research Guides are:

• Dinosaurs
• Knights And Castles
• Mummies And Pyramids
• Pirates
• Rain Forests
• Space
• Twisters
• Twisters And Other Terrible Storms
• Dolphins And Sharks
• Olympics Of Ancient Greece
• American Revolution
• Sabertooths And The Ice Age
• Pilgrims
• Ancient Rome And Pompeii
• Tsunamis and Other Natural Disasters
• Polar Bears And The Arctic
• Sea Monsters
• Penguins and Antarctica

Photograph by shortfatkid.