In a work subtitled ""The Secret of the Smile,"" readers learn a lot about Leonardo da Vinci, but little about his painting of the woman called Mona Lisa. Leonardo, as he is generally known, ""represents the spirit of the Renaissance""; this book explains to young readers his diverse talents. Even as a child, he puzzled his teachers with his many questions and with his unusual backwards writing. Galli presents Leonardo as an approachable, somewhat eccentric figure, one who delighted in masterminding extravagant festivals and designed his own clothing for comfort instead of style. Mona Lisa makes her entrance in the last three pages; she had a ""magical smile,"" and so Leonardo did what ""had never been done before--he painted what he saw."" That message may be too enigmatic for the picture-book audience, but they'll like the odd perspectives found in the soft, pastel-flecked illustrations, which mimic the hues of Renaissance fresco painting and, along with the pictures' humorous bent, give the work an airy quality. Some additional facts are provided at the end, but no specific references are cited.