Castle is just plain fun. Their cases can actually be pretty interesting sometimes, but the true gem of this series is the interaction between the characters. The cast play off of each other flawlessly.
Captain Montgomery: The Feds say he's a white male, 25 to 45 years old. Richard Castle: Could be me. Captian Montgomery: With a dysfunctional relationship with his mother. Richard Castle: Still me. Captain Montgomery: He has a menial, unimportant job.