Grief
Grief is one of the most significant themes in Dear Edward. After the tragic plane crash, Edward is primarily grieving the loss of his parents. He is also grieving the losses of those who died in the plane crash. Edward feels connected to those who died in the crash and their families and mourns their losses as well. For Edward and everyone else involved in the plane crash, grief is a complicated process. And for Edward, it takes him quite a bit of time (and a lot of help, especially letters written from the families of those who died in the crash alongside Edward's parents) so that he can fully grieve the tragic loss of his parents and the loss of the rest of the people in the crash.
Tragedy
Edward is the survivor of an unimaginable tragedy: a plane crash in which everyone, including his parents, but him died. This tragedy radically altered Edward's life, the lives of the family of the people who died in the crash, and the lives of the people across the United States. In different ways, the tragedy touched the lives of quite a few people.
For Edward, who experienced the tragedy firsthand, his life changed significantly as a result of the tragedy. For one, Edward went to live with his aunt and uncle. Edward also struggled with PTSD as a result of the plane crash and spent much of his life dedicated to healing from this traumatic event (and from the loss of his parents).
Growing up
After the crash, Edward had to grow up very quickly. Before the crash, he was a kid; after the crash, Edward was forced to be an adult. Under normal circumstances, kids gradually become adults. But Edward was forced to become an adult overnight so that he could contend with things only adults should have to deal with, like death. Part of growing up is finding out who someone is; Edward is forced to do that after he goes through the plane crash and with the help of his family, friends, and other survivors (in fact, Edward finds his future wife as a result of the crash).
