This meeting's book is Shade's Children by Garth Nix
Synopsis from B&N website
In the brutal world of the future, an unspeakable fate awaits the human children of the Dormitories when they turn fourteen. It is from this Sad Birthday that Shade's Children'Ella, Drum, Gold-Eye, and Ninde'have escaped. Hunted ceaselessly by savage mutant creatures, they join forces to form a resistance movement. Cunning, clairvoyance, and sheer desperate force of will help them. But ultimately their fate rests with the charismatic Shade, who calls himself their friend . . .