Elsewhere by Gabrielle Zevin
The novel explores the afterlife through the eyes of fifteen-year-old Liz Hall, who finds herself in a place called Elsewhere after dying in a hit-and-run accident. In this unconventional heaven, people age backward from the point of their death until they become babies again and are sent back to Earth to be reborn. Struggling with her new reality, Liz watches life on Earth moving on without her and must learn to let go of her past and embrace the unique cycle of life in Elsewhere. Along the way, she makes new friends, finds a new purpose, and experiences the complexities of love and loss from a perspective that challenges the living's understanding of death and time.