Remy is one of a handful of choristers on the submarine Leviathan, the only safe place for the faithful in a post-nuclear world. The "Topsiders" are all at war, fighting for resources, and the crew of the Leviathan must survive on the few things they can gather from the ocean, or steal from military ships above. Or at least, that's what Remy's been taught. But there are also secrets aboard the Leviathan, including the fact that Remy is a girl — the only one on board, brought because of her angelic voice — and as she learns more, she begins to doubt the stories she's been told.
A blurb on the cover of this book refers to it as "claustrophobic suspense," which I completely agree with. While the plot is something that can easily be compared to suspense and even dystopian young adult novels, the submarine aspect lends to a tighter sense of being trapped (both mentally and physically) than I've read in a long time. It's an intriguing story, and well worth the short time it'll take to read it.