**Arclight is about a boy and a girl**
Or, more accurately, a girl and a boy. Marina and Tobin, to be exact.
It may sound cliche that in the beginning they don't get along, but this isn't some story contrivance where the entire world rests in keeping two fated lovers apart. It's nowhere near that complex -- Tobin's father is dead, and he died protecting Marina. (Not a spoiler; this is established up front.)
Tobin can't look at her without remembering that his father is dead because of her. Marina can't look at Tobin without knowing she cost him his father, so to her, she's done to him what the Fade did to her. They're opposing forces caught in a common orbit around the memory of the same man, and so they can't escape each other. If Marina abandons Tobin, then she can't repay the debt she thinks she owes him in his father's name. If Tobin abandons Marina, his dad died in vain, so it's an antagonism that feeds on itself.
By now you're probably wondering if there's not a romance somewhere in all of this, and the simple answer is yes. The more complicated answer is -- define romance.
You have to read the book to understand what I mean by this, because explaining it outright would be a major spoiler, but I'll put it this way: think less triangle and more Möbius strip. When you're dealing a character who can barely remember her own name, then the idea of falling in love has to be handled carefully, lest it come across as a connection of convenience, rather than true emotion.