The #1 bestselling chapter book series of all time celebrates 25 years with new covers and a new, easy-to-use numbering system! When Jack and Annie came back from their adventure in Magic Tree House #15: Viking Ships at Sunrise, they had lots of questions. Why did Vikings go on raids? Did they really wear horned helmets? What were Viking ships like? Find out the answers to these questions and more as Jack and Annie track the facts about Vikings. Filled with up-to-date information, photographs, illustrations, and fun tidbits from Jack and Annie, the Magic Tree House Fact Trackers are the perfect way for kids to find out more about the topics they discover in their favorite Magic Tree House adventures. And teachers can use Fact Trackers alongside their Magic Tree House fiction companions to meet Common Core text pairing needs. 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 Have more fun with Jack and Annie at MagicTreeHouse.com!