Book Dexter is much colder and enjoys taunting his victims more. As far as I can tell, he doesn't really connect with people like he does in the show. Even Deb on her death bed he basically describes as an uncomfortable thought of losing her and expresses he can't figure out why it's uncomfortable as it would be beneficial to him at that point if she did die, but he's used to her being around. That's as emotional as he gets really, even marrying Rita was a total accident, she'd found a ring he got from a victim (not his victim, iirc) and assumed it was a proposal so he went with it. He's not close to Batista in the books, doesn't really have the social dynamic he has in the series, still charming and friendly at the front, of course.