Melissa Welliver 
Undying Tower [EPUB ebook] 

Decades after the discovery that a small percentage of the population has stopped ageing, the Avalonia Zone is in crisis. The ‘Undying’ have been blamed for the state’s problems. When Sadie takes the fall for an attack by a rebel group, she suddenly finds herself thrust into a cold and cryptic ‘correctional facility’ — The Tower. Here she’ll have to rethink everything she’s been told.