Definition: "Dexter" is a novel by American author Dean Koontz that was published in 1987. The book tells the story of a young man named Dexter O'Donnell who starts a "secret society" to help him become more powerful and understand his inner self. The protagonist, Dexter, is a troubled teenage boy who has had an intense relationship with his father, who died when he was very young. He becomes obsessed with a new girl in school and tries to take her away from him, but fails every time. When he finally succeeds in taking the girl from him, he discovers she's actually his twin brother, Dexter. Dexter is eventually able to break free from his father's control over his life and learns that his true identity was always there all along - he has always been Dexter. He also learns that it's important to keep your friends close, because they are the ones who will protect you if you're ever hurt or lost. The novel explores themes of family, love, self-discovery, and personal growth in a unique way. It is known for its fast-paced plot, complex characters, and vivid descriptions of urban life.

Dexter