Meet Jackie Robinson and solve a mystery in the #1 bestselling Magic Tree House chapter book series! PLAY BALL! Jack and Annie aren't great baseball players . . . yet! Then Morgan the librarian gives them magical baseball caps that will make them experts. They just need to wear the caps to a special ballgame in Brooklyn, New York. The magic tree house whisks them back to 1947! When they arrive, Jack and Annie find out that they will be batboys in...