The #1 bestselling chapter book series of all time celebrates 25 years with new covers and a new, easy-to-use numbering system! Jack and Annie are off on another mythical mission at the request of Merlin the magician. Luckily, they have a young sorcerer, Teddy, to help them. From underwater caves to a Spider Queen, from mystical selkies to a magical sword, this is a Magic Tree House adventure kids won't want to miss! Formerly numbered as Magic Tree House #31, the title of this book is now Magic Tree House Merlin Mission #3: Summer of the Sea Serpent. Did you know that there's a Magic Tree House book for every kid? Magic Tree House: Adventures with Jack and Annie, perfect for readers who are just beginning chapter books Merlin Missions: More challenging adventures for the experienced reader Super Edition: A longer and more dangerous adventure Fact Trackers: Nonfiction companions to your favorite Magic Tree House adventures