I stopped watching very early on, and only picked it up again for the very last season, so I'm no expert, but: my memory from both watching & conversations is that there was a lot of not-in-books nudity and sex, and it felt like it was there only because HBO felt the need to show that it was different than regular broadcast TV. It was totally gratuitous titillation - "instead of having exposition over here, why don't we have it over there with naked prostitutes in the background?" Later seasons didn't try so hard to be edgy AFAIK.