Medieval mysteries (Avi)

Night after night, a ghost appears in the royal castle of Pergamontio, terrifying the princess. Mangus the Magician doesn't believe in ghosts, but still the King charges him with finding this one and freeing his daughter from its torment. If he can't, Mangus will pay with his life. The magician's only hope is his faithful, street-smart servant boy, Fabrizio, who must solve the mystery of the ghost using logic and reason -- and a bit of magic of his...

Mangus the Magician and his thirteen-year-old servant, Fabrizio, are commanded to go to Venice, on pain of death, to find a book by Friar Luca Pacioli which reportedly contains a magical means of making money; but Venice is a strange and dangerous city, and someone else is also after the book--then Mangus is arrested, and taken to the prison, and Fabrizio and Bianca, an orphan he has met, must find a way to secure the book, save Magnus, and themselves....