Two teens must master the "art of killing" in this New York Times bestselling, Printz Honor-winning series from Neal Shusterman--all four books are now together in a collectible paperback boxed set! Thou shalt not kill: A world with no hunger, no disease, no war, no misery. Humanity has conquered all those things and has even conquered death. Now scythes are the only ones who can end life--and they are commanded to do so...