Exactly how steamy is this story?
PG-13
Brotherly Love
Sorry, Simon, but there's only one big kiss in this book and it's between Jace and Clary.
In the first half of the book, Simon kisses on Clary while she thinks of Jace and grocery shopping and doing her nails, so it's not that interesting. They even sleep together, but it's a clothes-on, slumber-party affair. Yawn, indeed.
However, once we end up in the Seelie Court in front of the Faerie Queen, the Queen demands that Clary receive "the kiss that she most desires" (2.8.388). And this being Clary, she most desires tonsil hockey from her own brother. So Jace kisses her, and the smooch scorches up about half a page. Yowch.
Afterwards, the sexual tension between brother and sister is higher than anything in Flowers in the Attic. Jace takes a shower back at the Institute and Clary can't take her eyes off Jace's hipbones, hipbones so sharp they could cut a girl if she gets too close:
His jeans were soaked and hung low on his hipbones. […] He was shirtless and barefoot, damp jeans riding low on his hips, showing the deep indentations above his hipbones. (2.9.9)-(2.9.18)
#demhipbonestho
Soon the conversation shifts to Jace and Clary consummating their relationship. Jace is all for it, and, frankly, the incest aspect of it doesn't bother Clary at all. She's bothered by what other people might think. They might be grossed out. This angers Jace, who snaps,
"What we feel—what I feel—it's sickening to you?" (2.9.64)
…and he throws up a wall between them. By the end of the book, Jace tries to move on (and Simon already has) so Clary is left kissing no one.