Obviously, if you haven’t read the book, there will be spoilers; I’ll try to spoilerbox anything really major.
I watched and greatly enjoyed the first season of Dexter on Showtime, and finally got around to getting the book Darkly Dreaming Dexter by Jeff Lindsay. I enjoyed the book, though not as much as the series. Some of the story elements from the series seem like they might be part of the second Dexter book, Dearly Devoted Dexter or possibly even the third book, Dexter in the Dark, although I can’t say for sure, as I haven’t read them. My reasons for thinking this:
For one thing, Paul is nowhere to be found and the Rita storyline is almost a non-factor. Also, Deb doesn’t have any dating life in this book, with or without serial killers.
Some of the characterizations are much different, and characters like Angel and LaGuerta are much more developed in the Showtime series, This is partly because the books are narrated entirely from Dexter’s point of view, so there are no scenes of Angel and his ex or political battles between Captain Matthews and LaGuerta. In the series, LaGuerta is portrayed as a tough but compassionate cop who is maybe a bit too headstrong at times; in the book, she’s an incompetent bungler who couldn’t solve a crime to save her life. LaGuerta also doesn’t survive the first book, being killed by Brian. Doakes is constantly creeped out by Dexter (much like the series) though there are no physical confrontations between them and Dexter senses that Doakes has his own “Dark Passenger” hidden beneath the surface. There is no “Rudy” persona for Brian; he doesn’t appear until the final showdown and reveal. Makes me wonder if Deb does end up dating the bad guy in the second book…
The final showdown is handled much differently as well; While the series ends with an almost poetic dispatching of Brian by Dexter and has Deb under the impression that Dexter saved her life, snapping awake at the very moment that Dexter stops Brian from stabbing her, in the book Dexter finds Deb strapped down and Brian’s there and very nearly convinces Dexter to kill Deb. Dexter ends up struggling mightily between his attachment to Deb and his desire to kill, and he very nearly does stab her, and she’s awake the entire time. She actually has to talk him out of killing her, and in the end it’s only Harry’s words, “choose what or who you kill” that snap him out of it. Brian ends up killing LaGuerta and then escaping. Not nearly as satisfying or plausible as the series, IMO.
Dexter has far fewer kills in the book, as well, though it’s made much clearer that Dexter really is a monster, that it’s only Harry’s code that keeps him from killing at random and without regret.
Overall, I’d rate the Showtime series 8 or 9 and the book (the first book anyway) a 6. Enjoyable, but not up to the level of the series, in other words.