About a dozen books were displayed under the heading "Teen Dystopia Sale." Checking out the titles, I learned this means exactly what it says -- these are books about "dystopias," or bad times, written for teens. A "utopia" is a paradise, a dystopia its opposite. The most well-known title on the endcap was Mockingjay, the concluding volume of Suzanne Collins "Hunger Games" trilogy. All three of those have been top sellers. In the trilogy, a semi-totalitarian government deceives people and drafts teens for a kind of "survival of the fittest" tournament pitting them against teens of other districts.
I didn't recognize the others, but they shared the same kind of worldview -- a totalitarian state, either along 1984 or Brave New World lines, that controls people's lives until challenged by a brave young person or group of them. If I remember anything at all about being a teenager, I can see exactly why these kinds of books are popular. If I thought about it, I probably realized that parents, teachers and bosses weren't really cruel and ruthless dictators, but I bet I didn't spend a lot of time thinking about it whenever one of them didn't allow me to do something I wanted.
I imagine the books also speak to something that kids share with adults -- a deep desire to matter, to do something that makes a difference. In a world in which you are subject to so many unfair! rules that are not your own, it can be even easier to feel as though you don't matter than it is for adults.
As for the books, I'd bet they parallel a lot of genre fiction -- some top-level work, some that's good storytelling if kind of lightweight and a load of stuff that one day the Ents are going to want an accounting of when we total up how many trees it took.
I'm not sure about the contest Hastings was running, though. If you win, you get a 20-book pack of teen dystopia fiction -- and that seems like a whole lot of moping, even for a teenager.