Vanishing Act by John Feinstein

After solving a kidnapping/blackmail case at the NCAA Final Four in Feinstein’s first novel for kids, Last Shot, Stevie and Susan Carol are back. This time, the young sportswriters are invited to cover the US Open Tennis Championships. A comfortable two weeks of high-class sports? Think again. When one of the hottest young stars in women’s tennis is kidnapped before her first-round match, Stevie and Susan Carol are forced into action. Worse yet, evidence starts pointing towards Susan Carol’s uncle Brendan, agent for a rival young player on the circuit. Feinstein knows his sports, and he knows his mysteries. Before it’s all figured out, this one will have you moving your head back and forth like you were at a tennis match!