Book excerpt: In this second book of the Edge of Yesterday series, Charley Morton, girl inventor extraordinaire, is determined to hack time. When her model for a time machine accidentally ignites, Charley's sent whirling back 500 years, coming face-to-face with her Renaissance idol, Leonardo da Vinci. It's a perfect scenario for the Renaissance-girl wannabe. Until the news: Her mother is gravely ill. Charley must get home! Can she reverse-engineer time travel . . . and what future will she encounter if she succeeds?