As if 17-year-old Alexandra Lucas' anxiety disorder isn't enough, mysterious holograms suddenly appear, heralding the end of the world. They bring an ultimatum: heed the warning and step through a portal-like vertex to safety, or stay and be destroyed by a comet that is on a collision course with Earth. With the deadline of the holograms' prophecy fast approaching, Alex feels as though she is living on a ticking time bomb, until she discovers it is much, much worse. From $7.99 SHOP NOW /