This is my second favorite show of all time (after Breaking Bad...) At first I was put off by the premise of having a television show where the protagonist is a serial killer. That sounded reprehensible. I mean, c'mon, are they trying to make serial killers look cool now? What is this world coming to? That's what I thought, but the show works because the whole dark serial-killer thing is compensated for by everything else in the show: the colorful, sunny, Miami setting, the relatively wholesome family values and themes about justice and protecting the innocent. The first few episodes put me off a bit with how gruesome and gory some shots were, but later the directors made a good decision to minimize that; For the most part the show doesn't dwell on the violence, and it happens tastefully off- camera.
I love this show, but Dexter is the least-convincing psychopath in the history of TV psychopaths. Throughout the series he behaves in a way that is far more reasonable, thoughtful, and considerate than most 'normal' people. True psychopaths are selfish and impulsive. Psychopaths are born, not made by traumatic childhood experience. Pyschopaths are supposed to be charismatic, impulsive, reckless, while Dexter is just kind of socially awkward in a way that is far more normal than he realizes. Psychopaths generally don't have an urge to kill, they just have no remorse or empathy about it. To a psychopath killing a person is like squashing a bug. In his inner monologue in multiple occasions he says/thinks nonsense along the lines of "If I could love anyone, I'd love my sister Debrah." or "If I had feelings, I'd feel bad in this situation." When obviously if he didn't have those feelings, those thoughts would very unlikely to occur to him. Given the tone and situations where he says that, he seems less like a psychopath and more like someone who has a warped view of themself and their feelings.
Dexter is not realistic, but the writers have successfully created a protagonist that is a symbol - exaggerated for story-telling purposes - a symbol of a regular person like you or me, who has demons to battle and struggle against every day. He's just a regular person who struggles with balancing work and family and a terrible addiction. This show explores the ultimate fear that is too common: The fear that if other people learn who we really are, they will all hate and shun us. Most people have more boring secrets: that they are an atheist, they are gay, they like to eat icecream straight out of the carton with potato chips late at night, but deep down inside in our inner dramas, it feels like we might as well be serial killer and so we can relate. But what really keeps you watching the show is you really want to see these bad guys caught one way or another, and you really don't feel bad when they end up on Dexter's table.
This show goes on for 8 whole seasons. It seems like everyone complains that the show jumped-the-shark after the first season, or the second season, or whatever. Personally, I enjoyed all the seasons. They tend to follow a formula, it's a good formula: Every season there is a Big Bad that Dexter and the police hunt down. Dexter always makes a new friend that gets his hopes up that he finally has someone he can confide in and have a rapport with. Throw in a love interest, some family drama, and some minor side-plots about his police coworkers. It's all good except sometimes the side-plots can seem rather pointless and tacked-on. And Dexter/Michael Hall has no chemistry with his love interests. I seriously expect him to come out of the closet now that the show is over. But overall the acting is amazing, there is never that feeling that I'm just watching a show with actors. It's not realistic per-se, but it's immersive.
It was only until season 8 that I really felt like the show was getting contrived and was outliving its worth. But first thing's first, the early seasons are by definition, classic good ol' Dexter. But season 4, with John Lithgow as the most excellent Big Bad of any season, is not to be missed. Over time as Dexter eventually confronts people like big-time mobsters and super-rich dudes, his whole socially- awkward insecure serial killer schtick starts looking kind of quaint in comparison. Then the show ended... I won't spoil it but I was a little surprised and slightly disappointed. The ending left some side-plots hanging. They introduce important new characters and then just forget about them. It wasn't bad, but the writers fumbled the ball there.
But despite my criticism, I love this show and would recommend it. It's smartly written, engaging and suspenseful, and has lots of heart for a show about a serial killer.