The #1 bestselling chapter book series of all time celebrates 25 years with new covers and a new, easy-to-use numbering system! The magic tree house leads Jack and Annie to a tiny deserted island in the middle of the ocean. The brother and sister team are soon rescued by a ship of explorers and scientists who are looking for...a sea monster! Formerly numbered as Magic Tree House #39, the title of this book is now Magic Tree House Merlin Mission #11: Dark Day in the Deep Sea. 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