Xibalba

Xibalba is the name of the society that the kids in the novel create after the Day happens and the vast majority of the population disappears, leaving only a few dozen teens and preteens. The society has all the things the kids need to survive, and everyone assumes a role within it to provide things for the others and trade their goods and services for those of others. The fact that it is so robustly put together is proof of what humans can do when faced with a huge trauma or difficulty.

Martin's island

At the beginning of the novel, Martin lives on a remote island in solitude with his father while he works on a mysterious machine whose purpose Martin does not understand. At least for much of that time Martin has a compatriot even though not many people live there; plus, he meets a boy named...