Dexter is a monster! So to speak.
I remember hearing about the premise of the show before it aired, and I thought 'That's just stoopid!'. A friend showed me the first four episodes, and I was hooked. Really well done, and Michael Hall does a great job with the character. Good ensemble cast. The writing is really top notch.
I liked the first season best, then the third, then the second, but they are all well worth watching. It was a tough premise to make a sympathetic character with, but boy did they do it.
I have just finished reading the first novel that it was based on, and it suffers in comparison to the show. However, some of the really zingy one liners from Dex in the first season were lifted directly from the book.