Gone, by Michael Grant. This book is about a boy called Sam. One day, out of the blue, everybody over the age of 15 disappears. Gone. Poof. There seems to be an dome-shaped barrier around them. At that moment, some kids develop powers, aka, Superhuman speed, tele-potation, light, energy balls. Sam, has to help take care of the younger kids, ration out food supplies and stop Caine, his half brother and his bunch of thugs from killing, murdering capturing and abusing the other kids. Will they make it? Find out more in the Gone series.