That show is all about the characters, and even then, that can get pretty thin. I trudged through both seasons in a week a couple months back, and S2 was really rough to finish I remember.
Also, I could never get over the idea that I was supposed to be rooting for Dexter, as they loved to paint him as some Batman/Punisher anti-hero type most of the time, stock with his own origin story played out over S1.
From what I heard, the third book in the series really takes a dump on everything and went all supernatural, Dexter's killer obsession had something to do with some demon who fed off his whatever. Shit you not.