Present day reception of Emily Dickinson's somewhat morbid and obsessive focus on the theme of death is distorted by our lack of appreciation of how current the topic of death was in her life and times. During her life, death was a constant preoccupation. People died from a variety of diseases, such as tuberculosis and pneumonia. Likewise, even childbirth and pregnancy were potentially fatal conditions in those days. Thus death was far more in the public consciousness compared to the taboo subject that we have made it today.
However, within this focus on death, it is important how Dickinson brings her customary wit and irony to play in examining death from a variety of different standpoints. For example, in "I heard a Fly buzz--when I died--" the traditional idea of death as a release from the pains and sufferings of life and the way in to eternal paradise in heaven is probed by the appearance of a "fly" with all of its connotations with death and rotting corpses. Death is likewise personified in a number of different ways that challenges the stereotypical representation of death. Most famously, of course, Death is personified as a polite gentleman caller in "Because I could not stop for Death," but also as a dangerous, threatening yet passionate figure in "Death is the supple Suitor."
So, whilst we can definitely say death is a major theme in her work, we would do a horrendous injustice to treat this as some kind of obsessive necrophilia. Dickinson explores the one unknown territory of humanity in a multifaceted approach that questions, challenges and pokes fun at the way death was considered in her day, and indeed in our day today.