"In Search of Klingsor" is a historical novel that revolves around the pursuit of a mysterious Nazi scientist named Klingsor. The story is set during World War II and the Cold War, and follows two main characters, an American physicist and a Mexican mathematician, who are tasked with finding and identifying Klingsor. The novel uses real historical figures and events to explore themes of science, war, and morality, while also delving into the complex nature of truth and deception.