The first novel in the Dexter series felt like a watered-down version of season 1 of the TV show. I suppose this isn't a fair judgment, as the show is based on the book series, but that's what it seemed like. The novel had a lot of high-tension, suspenseful moments, though, and Dexter's inner monologue with his "Dark Passenger" (the part of his psyche that urges him to kill) was insightful. 
 The ending of the book definitely diverged from the show, and I'd be interested to read book two to see where Lindsay takes it. I did have some logistical problems with the novel's end, but maybe they're explained in the next book...