Skeleton Key by Anthony Horowitz

In this thrilling young adult adventure, a teenage spy is sent on a mission to investigate a reclusive ex-Soviet general who has settled on an island named Skeleton Key, off the coast of Cuba. The protagonist uncovers a dangerous plot involving a catastrophic weapon with the potential to unleash a nuclear disaster. Teaming up with two American agents, the young spy must navigate a series of perilous encounters, outwit the general's sinister plans, and prevent a global catastrophe, all while maintaining his cover and trying to survive the deadly game of espionage. The 9495th greatest book of all time