I have somehow avoided seeing or even really hearing anything at all about the tv series (except "It's about a serial killer"), despite having several family members that are moderately obsessed, so it was interesting walking into this with no real understanding of what on earth I was going to find.
It was interesting.
I'm not sure I get the huge hubbub surrounding the show and books, but it was an enjoyable read. Dexter is certainly an intriguing character, and has quite a few demons to fight, including several even he didn't know about.
His cleverness and the fact that he is very aware of what he is and what that means and how he needs to handle things makes everything he does and is a little more bearable, given he's kind of the hero. It does raise questions of what makes a genuine hero, though, because I kind of feel like maybe he should not qualify, but I can't exactly sort out how to explain why.
The mystery was intriguing, and I didn't actually see the ending at all until quite late in the game, so that was a bit of a surprise. I do love that. The book has some mystery, but is pretty disturbing both for imagery and psychological reasons, so I'd almost consider it less of a thriller and more of a horror novel. Debating the semantics of where to place novels is moderately moot, though: it's a book about a serial killer, and he's the good guy. Make your judgment on whether it is a good fit for you or not based on that.
I'll probably pick up a few more of the series at some point, but I'm not in a huge rush (and I'm certainly not up for devoting myself to the series, which is probably a much bigger time investment). I can't make comparisons between the two, but if you like the idea or enjoy the series, this is probably worth picking up and trying.