Jameson Rook is a fictional character Richard Castle created for his Nikki Heat series of crime novels.
He is a famous magazine journalist who shadows the main character, Detective Nikki Heat, as well as her on-again off-again love interest. The character moonlights as a romance novelist under the pen name Victoria St. Clair. He is based on Castle himself and the way he works with Kate Beckett. ("Nikki Heat")