Villains Die At Eighteen

I've read a lot of novels in my life but out of all of them, Hellscape was my favorite. The world itself had an engaging framework. All villains are stronger than heroes. However, inevitably, they will all die before or precisely at their eighteenth birthday. Because of this balance, the whole world was in a standstill age of war and violence, thus justifying the book's title. Why, out of all the damn books I read, did I end up here?