Dexter really hasn't delivered after season one.
And I agree with Bret Easton Ellis, a politically correct serial killer is a little weak.
Season 1 was based very closely on the first book, there are very few differences. The rest of the seasons are nothing like the book apart from the dexter character. I think the show is still pretty strong, especially seeing as how the books are getting worse.
Lindsay is probably putting all his creativity into the series, his writing in Dexter is Delicious came across as so forced, it was actually the first one in the series that was difficult to get through, even Dexter by Design and Dexter in the Dark were easy to get through despite their awful plots. Dexter is Delicious was just all round trash.
I remember when I read Darkly Dreaming Dexter I was totally enthralled in it and even the story line was great, Dearly Devoted Dexter was great too and I was dreaming of the day it came to life on the screen. The first series was awesome, second and third lost me a bit, but the fourth and fifth were great, which almost made up for the books getting so shit.
That said I'm 5 years older than I was when I read the first book, maybe I just don't like the latest ones because I'm old. However, I am still going to buy Double Dexter as soon as it comes out.