Grief (novel)
During the course of the novel, the ideas of the stages of grief are introduced. The stages are denial, anger, depression, and acceptance. The narrator, as well as other characters in the story, slowly passes through these stages in trying to deal with death.
Ambiguous loss
The difference between regular grief and grief from an ambiguous loss is the type of loss creates the type of grief experienced. Grief in ambiguous loss can be both beneficial and difficult. Since the grief in an ambiguous loss differs than the linear stages of grief there is no pressure to move on or achieve closure, and this allows for people to remember the lost loved one and move on with relationships and life. There are three specific types of grief that can develop from the type of ambiguous loss. 
Anticipatory grief occurs before bereavement, mourning after death occurs, and upon realizing that death may be imminent for a loved one, anticipatory grief sets in. This type of grief is common among families who have a loved one living with Alzheimer's disease. The grief becomes anticipatory due to the knowledge that the loved one's mental state will only become worse, so the grieving process can start very early.