John Dies at the End is one of those books that started life as an internet phenom, then was re-bound and sold as a book. I'm usually leery of these things, but I decided to give it a shot (I've since found out that it was substantially fixed up before becoming a book).
Whatever its other literary merits, John Dies at the End pulls off the trick of being very funny and very scary at the same time, sometimes within the same paragraph. The closest thing I can think of is Buffy the Vampire Slayer, but even there the humor usually alternates with the horror; they don't come simultaneously. (And I'm not talking about "humor"; the jokes are actually funny).
I enjoyed Susan Collins's The Hunger Games more than I thought I would. It's one of those YA books that crosses the line to have adult appeal, even though it's clearly written with the teen market in mind. I think part of its success is that Collins has been pretty ambitious, throwing in a lot of classical references (Theseus, Spartacus, Romeo & Juliet) that I can't help but think go over the heads of most kids. Like the way that the major antagonist in the Games is called Cato, even though all the other Tributes have non-Roman names. But for kids who can't tell a Roman name from a non-Roman one, does this have any resonance?