Skeleton Key (Alex Rider) by Anthony Horowitz
This is the third book in the Alex Rider Series. It is a little more violent than the first book, and there is more action. It is fast paced and well written. It is a good action novel. One nice thing about the Alex Rider Series is that each book is a separate mission and a complete story. You can read any book in the series in any order.
Alex volunteers to be a ball boy at Wimbledon, and quickly uncovers a plot by an Asian gang to rig the tournament. The gang sends a professional killer after Alex who must then go into hiding until the agency can get the contract cancelled. The spy agency sends Alex to Cuba, where he must pose as the son of two American CIA Agents. The CIA Agents are tracking an illegal uranium shipment payed for by an ex-Russian General who still believes in a communist Russia. When the Agents are killed in the line of duty, Alex must complete the mission on his own.