"Many hundreds of years ago, the city of Ember was created by the Builders to contain everything needed for human survival. It worked... but now the storerooms are almost out of food, crops are blighted, corruption is spreading through the city and worst of all -- the lights are failing. Soon Ember could be engulfed by darkness...But when two children, Lina and Doon, discover fragments of an ancient parchment, they begin to wonder if there could be...

After obtaining an ancient book with only a few pages remaining, Lina and Doon return to Ember seeking the machine described in the book that might be able to aid their new community, Sparks, through the winter.

From New York Times bestselling author Ben Hatke comes Things in the Basement, a young readers graphic novel about Milo, a young boy who discovers a portal to a secret world in his basement.
It was supposed to just be a normal basement—some storage boxes, dust, you know, the usual basement stuff. But when Milo is sent by his mother to fetch a sock from the basement of the historic home they've moved into, Milo finds a door

...

Will Burrows believes he is safe at the very center of the earth, in a world that no one knows exists, but the Styx are close behind and will follow him anywhere, while on the surface, Drake and some unlikely allies unearth some critical secrets.

Thirteen-year-old Sully Stringfellow, his arch-nemesis Izzy Cisco, friend Moleman, and a league of long-forgotten plumber heroes team up to save Nitro City from mutant creatures in the sewers.

The outer crust is under attack by the subterranean Styx who are turning ordinary humans into walking bombs and incubators for their eggs, and only Will Burrows and his band of retired commandos stand in their way--but the Styx also have problems of their own.

Teenager Eliza and her friends are going to explore a cave near their upstate New York home, but first her friends insist on dragging her to Drowner's Swamp, a bog legendary for its dangerous sinkholes, and a place which her mother has frequently warned her about; Eliza does not want to go, and when the earth opens up and swallows her she finds herself in a system of caves--and what she finds living there is strange and dangerous beyond anything the...

A completely implausible earthquake sets Frederik Sandwich and Pernille, a mysterious stranger, on an adventure through secret and forbidden places in their small town.

As two children and their pet gazelle sneak out of the house in search of treasure, they come across a world beneath the city that is inhabited with monsters and pirates.

"When Hyacinth mixes hot and cold water in a sink in London with disastrous results, she learns that the city was built on magical rivers that are now London's sewers--and somehow her family is connected to the magic"--