22 books in series

Magic Tree House "Merlin Missions"

Magic Tree House "Merlin Missions" is a 22-book series with 22 released primary works first released in 2001 with contributions by Mary Pope Osborne.

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
Moonlight on the magic flute
A Crazy Day wth Cobras
Dogs in the dead of night
Abe Lincoln at Last!
A Perfect Time for Pandas
Stallion by Starlight
Hurry Up, Houdini!
Soccer on Sunday
Shadow of the Shark
Balto of the Blue Dawn