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 to save Merlin from his sorrows! The brother-and-sister team travel back in the magic tree house to the period known as the Renaissance. This time, Jack and Annie will need more than a research book and a magic wand. They’ll need help from one of the greatest minds of all time. What will they learn from Leonardo da Vinci?

Formerly numbered as Magic Tree House #38, the title of this book is now Magic Tree House Merlin Mission #10:Monday with a Mad Genius.