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 arrive on the one continent they haven’t visited before: Antarctica! What can they hope to learn about happiness in such a barren place? Only the penguins know for sure…Jack and Annie are about to find out! Formerly numbered as Magic Tree House #40, the title of this book is now Magic Tree House Merlin Mission #12: 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 Super Edition: A longer and more dangerous adventure Fact Trackers: Nonfiction companions to your favorite Magic Tree House adventures