At its core, all literature explores the essence of human existence or the human condition. Life and death are arguably the most pivotal elements of humanity, leading many literary pieces to explore these themes. The Lovely Bones raises two fundamental questions: "What does it mean to be alive?" and "What does it mean to be dead?"

As Susie learns what it means to be deceased, she is also forced to confront the essence of life. Her deepest sorrow stems from realizing she can no longer participate in the physical world—that she cannot experience life as she once did. The novel highlights the physical experience as a crucial component of living. Although Susie, now passed away, lacks this physicality, she can still feel emotions such as longing, hoping, and yearning. Sebold blurs the line between life and death, as Susie is keenly aware of her demise and knows she exists in a realm distinct from Earth, yet not completely detached from it. Susie's heaven mirrors Earth more than a celestial paradise, featuring earthly activities like enjoying ice cream, playing with dogs, and residing in a duplex.

The story depicts life as a series of transformations, each involving the body and the physical surroundings. Physicality emerges as the hallmark of life. Susie's ability to progress in her heaven, or in her death, depends on her return to Earth. Though her return is without a body, when she inhabits Ruth's body, Susie "realize[s] that the marvelous weight weighing [her] down was the weight of the human body." Susie grasps the transient nature of this physicality, which may be one of Sebold's central messages.