The New Immortals

Most books Nicky had read about the afterlife gave the impression that when you die young, you die painfully, waking up in the afterlife still fighting. In reality, the transition is effortless for Nicky - she isn't even able to say why she is there in the first place. However, her death leaves her with unfinished business and many unanswered questions, not least of all the unknown circumstances of her death.
Nicky decides she isn't ready to die, and begins a quest to make it back to reality. However, her actions may cause the biggest upheaval in the natural order that anyone has ever seen - either in this world or the next.