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 on a mission for Merlin the magician! This time, the magic tree house whisks them off to Thebes, Egypt, to find Florence Nightingale, a world-famous nurse. But when they find her, the Florence Nightingale they meet is not a famous nurse at all--she's not even a regular nurse! Have they found the right person? Or did Merlin make a mistake? An easy mission turns dangerous when Jack and Annie try to solve the mystery! Formerly numbered as Magic Tree House #51, the title of this book is now Magic Tree House Merlin Mission #23: High Time for Heroes. 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