Magic Tree House:
Merlin Collection

 #30 Haunted Castle on Hallows Eve
#31 Summer of the sea serpent
#32 Winter of the Ice Wizard
 #33 Carnival at Candlelight
 #34 Season of the Sandstorms
 #35Night of New the Magicians
 #36 Blizzard of the blue moon
#37 Dragon of the Red Dawn
#38 Monday with a mad Genius
#39 Dark day in the deep sea
 by
Mary Pope Osborne

 10 Brand New Hardcover