When Marvin Redpost agrees to go over to Casey Happleton's house, he doesn't know what he's in for. Casey shows him the magic crystal she has just found and offers to give Marvin a few wishes. Is the crystal really magic? Or is it too good to be true?

Louis Sachar is the bestselling author of the award-winning novel Holes, as well asSmall Steps, The Cardturner, Stanley Yelnats’ Survival Guide to Camp Green Lake, There’s a Boy in the Girls’ Bathroom, The Boy Who Lost His Face, Dogs Don’t Tell Jokes, and the rest of the Marvin Redpost series, among many others. Visit him at louissachar.com.