The City of Ember The diamond of Darkhold. Book 3

Lina and Doon escaped the dying city of Ember and have survived their first few months above ground. But it's winter now, and the harsh realities of their new world have begun to set in. When Doon finds a book that hints at an important, long-lost device, it doesn't take much for him to convince Lina to join him for one last adventure in the place they used to call home. After all, the book is eerily similar to the instructions that led them out of the darkness -- how could they not at least try to unpack its secrets? But will this mysterious technology be enough to help their people? And what -- and who -- will they find when they return?