50. Stormbreaker by Anthony Horowitz

This short book introduces Alex Rider, a 14-year-old hero of British author Horowitz's spy thriller. When his guardian and uncle, Ian, is mysteriously killed, Alex discovers that his uncle was not the bank vice-president he purported to be, but rather a spy for the British government. 
Now the government wants Alex to take over his uncle's mission: investigating Sayle Enterprises, the makers of a revolutionary computer called Stormbreaker. The company's head plans to donate one to every secondary school in England, but his dealings with unfriendly countries and Ian Rider's murder have brought him under suspicion. Posing as a teenage computer whiz who's won a Stormbreaker promotional contest, Alex enters the factory and immediately finds clues from his uncle.

Good short book, good main character, Alex Rider.