If you've watched Game of Thrones and read A Song of Ice and Fire, then you know that the HBO series and George R.R. Martin's books don't always line up. Some things get left out. Some things get added. Plenty of people have noticed one thing that gets added a lot: sensual stuff.
There are a lot of sex scenes in the show that aren't in the book. That's a fact, but there's two ways to interpret that fact. One view accuses the showrunners of inserting gratuitous sexuality for the sake of ratings and shock value. Some characters like Ros and Olyvar seem like they're added to the show just to flesh out the sex lives of other characters (like Petyr "Littlefinger" Baelish, Tyrion Lannister, Theon Greyjoy, Grand Maester Pycelle, Oberyn Martell, and Ellaria Sand, just to name a few).
The other view is a bit more nuanced. The book has many couplings that are important to the narrative but revealed through second-hand sources. To follow the plot, viewers need to know about them even if none of the main characters are actually present for the deed. And when that information needs to be revealed in a visual medium, showing is better than telling. So is it good storytelling? Or gratuitous smut?
To find out, you'll need to analyze all the most gratuitous sex scenes added to Game of Thrones that weren't even in the books.
In the show: In one of the most notably Skinemax-style scenes, Ros and Armeca put on a private show to give Littlefinger a sense of how they'd be in bed. He coaches in return, but it's not your typically seedy "casting couch" scene. He doesn't even get out of his chair. see more on Ros
In the books: After returning Tyrion to King's Landing and receiving a lordship, Bronn turns into kind of an upper-class jerk. He marries the homely Lollys Stokeworth and stays in his new castle. He doesn't spar with Jaime, and he doesn't go to Dorne to peep Dornish cleavage.
In the show: Bronn ends up incarcerated in Dorne with the Sand Snakes. Tyene Sand gives him a little peepshow to elevate his blood pressure and speed her poison through his veins. She saves him though, so the scene is kind of circular.see more on Bronn
In the books: Something like this is probably going on off-page because Lord Petyr Baelish seems to value the spying advantages of his brothels more than their earning potential. The book version of Littlefinger is practically asexual, so it's unclear if this would even interest him (unless the woman was Catelyn Stark).
In the show: Littlefinger peeps through a peephole to watch Armeca servicing a customer while said customer is peeping through a peephole to watch some girly action. It's an "Inception of Ice and Fire."see more on Petyr Baelish
In the books: Oberyn and Ellaria are a lusty couple who talk openly about their fluid identities. Oberyn is especially pansexual, but neither of them is ever a POV character, nor are any of their canoodling companions. So these scenes just aren't part of the books.
In the show: Oberyn helps Ellaria pick a professional (Marei) and then chooses Olyvar (even though he's not for sale) for himself, but before things get rolling, someone sings "The Rains of Castamere." You know Oberyn is always down, because he practically always wears a Hugh Hefner robe, but that song is his anti-mojo. Later, he tries to get Olyvar to get down with Ellaria, even though Oly doesn't swing that way. Tywin Lannister, the Hand of the King at this point, interrupts group loving numero dos.see more on Oberyn Martell