In this charming and classic story, four siblings are set to spend a hot, boring summer in the care of a babysitter, when they come upon a coin on the sidewalk. They soon realize that the coin has special powers, but in the classic tradition of wish fulfillment gone awry, it only does half the magic the children wish for. As can be expected, a series of strange and hilarious adventures ensues, and the children learn about thinking ahead to envision the consequences of their wayward wishes. What sets this book apart, however, is its pitch-perfect storytelling which draws readers in and keeps them guessing until the very last page. (Harcourt, $14.95)