Grief
Grief and the way that people deal with grief are pervasive throughout Our Share of Night. After the death of their beloved mother and wife (respectively), young Gaspar and his father are heartbroken. They loved their mother and couldn't even fathom losing her. But she died, causing them tremendous discomfort and grief. They spend much of the novel grieving her death; it is also her death that makes Gaspar and his father realize the importance of staying together and being a family. Grief is hard to deal with, but it can be unifying for some people.
Parental love
Our Share of Night shows the power and importance of parental love. In the novel, after the death of their beloved mother and wife (respectively), Gaspar and his father are on the run from an evil cult that wants nothing more than to bring up Gaspar to their ranks. Gaspar's father, however, loves his son and doesn't want him to be poisoned by the beliefs of the cult. To stop that from happening, he uproots his life and risks life and limb to ensure that his son is raised in a loving and normal environment that doesn't believe in cults or their values. This kind of selfless love is important to Gaspar and every child in the world because it shows them how important people are to each other.
Cult
Cults, which Britannica defines as "a small religious group that is not part of a larger and more accepted religion and that has beliefs regarded by many people as extreme or dangerous" play a significant role in Our Share of Night. In Our Share of Night, an insidious and violent cult called the "Order" which tries to bring Gaspar into their ranks. But Gaspar and his father don't want to join the cult, fearing that the cult's evil will infect them. The cult has radically altered the course that Gaspar and his father's life will take; to escape the grips of the cult, the two get in their car and start driving, hoping to live their lives according to their values, morals, and beliefs systems.
