The Overland - life on this planet, as we currently know it.
The Underland - a mythical place that exists in what I can only believe is an offshoot of the NYC sewer system.
And so we get into the Gregor the Overlander series.
Once again, I'm delving into the YA genre. Gregor the Overlander targets preteens, but would be suitable for anyone who can read chapter books, young and old alike. Gregor, the title character, is an 11-year-old boy living in New York City. He lives in a small, run-down apartment with his mother, father, grandmother, and two younger sisters, until the day that he follows his youngest sister, Boots, into a vent opening in the basement laundry room.
Gregor and Boots find themselves in the Underland, a land inhabited by humans, gnawers, nibblers, spinners, crawlers, fliers, and other such creatures. Humans are of normal size, but very different look, with pale skin, violet eyes, and silvery hair. The other animals are of gigantic proportions. Humans travel by flying on bats, and together fight an almost constant war with the gnawers (also known as rats). The largest population of humans is found in Regalia, the royal city of the Underland. It is there that Gregor is discovered to be the Warrior of the prophecy of Sandwich.
Gregor is the long-awaited warrior who will either save Regalia from the gnawers, or doom it to destruction. (After all, what is a fantasy book without and end-of-the-world prophecy?) But first, there are a few more prophecies that need fulfilling.
The series follows a series of prophecies, each more intricate and daunting than the last. The final book culminates in a war throughout all of the Underland, and only one side can win. Young adult book, or not, the ending thoroughly surprised me. And the relationships forged between the inhabitants of the fantasy land continue to intrigue me.