Castle is an American crime drama television series, which premiered on ABC on March 9, 2009. The series is produced jointly by Beacon Pictures and ABC Studios. Created by Andrew W. Marlowe, it primarily traces the lives of Richard Castle (Nathan Fillion), a best-selling mystery novelist, and NYPD Detective Kate Beckett (Stana Katic) as they solve various unusual crimes in New York City. Detective Beckett is initially infuriated at the thought of working with a writer and goes to great lengths to keep him out of her way. However, the two soon start developing feelings for each other. The show focuses on the romantic tension between the two lead characters, and also on the unsolved homicide of Beckett's mother.
I really recommend it highly. We are watching them in order on the DVDs we have (which you can purchase below) and the current season. It has quite a bit of humorous moments to break up the seriousness of what is going on, but they get the case solved.