The question for me, then, is how does Stewart do that? How does she build it up to the point where I, as the reader, am anxiously waiting for it? There are many romantic partnerships which I enjoy as a reader -- but only a few where I have a visceral reaction every time I read it. As a writer, I'd love to be able to write the latter (though I do realize it has to be somewhat a personal thing -- I mean, there are probably people out there who couldn't care less about Bryony, right?).
Part of the thing with Bryony, of course, is that her secret love turns out to be someone she truly wasn't expecting -- so the surprise element works well there, I think. I also like stories where the romantic leads appear to be at opposition to each other, fighting their attraction or keeping it hidden (or keeping it only between themselves and the reader). Anytime there's a strong reveal, I think that ups the ante.
I've also read a fair amount of sacrificial love, lately. That sounds good, on paper, but for me...well, I guess it depends on the execution. I think I'm so focused on a 'happy' ending that sacrificial love isn't always my favorite. And sometimes, in order to have a 'happy' ending with sacrificial love means that the relationship comes across as slightly contrived.
What about you? What kinds of romantic tension works best for you, and why is that?