Tesla's Attic, by Neal Shusterman & Eric Elfman
Loved the last chapter, after the world had been saved. "When it was clear that the earth was still here, and would remain here indefinitely, people got pissed off. Across the globe, valuable possessions had been given away, and guilty consciences had been purged by shocking confessions, all in the belief that no one would live to regret it."
Who wouldn't love a grownup like Mrs. Planck (that's right, as in Planck's constant). A smart little girl says "I was thinking that success is the best revenge." "No, dear," Ms. Planck corrected. "Revenge is the best revenge."
In between is Nikola Tesla and an asteroid, mathematics and physics. What's not to love?