Death is part of who we are. It guides us. It shapes us. It drives us to madness. Can you still be human if you have no mortal end?— Roran
Death is the cessation of life and an ongoing fact of the world of Alagaësia. The protagonist of the The Inheritance Cycle, Eragon Bromsson seeks to prevent death where possible by ultimately toppling Galbatorix, but must live with the stark reality that his own actions will cause many deaths, many of them dealt by his own hand. Eragon has already been affected by several highly personal deaths; first that of his uncle Garrow, later Brom and also Ajihad, Hrothgar and Oromis and Glaedr.
Within the Races of Alagësia
The human society in Eragon's culture has many differing beliefs and superstitions regarding the concept of death, but little unified religious structure on the matter. The human God of Death is Angvard. The dwarves belief in life after death, but only believed that one could go on to the afterlife after one is buried in stone. They believe that honored dwarves dien in the hall of Morgothal. The death must not be by their own hand, however, as Morgothal does not accept those who attempt to hasten their entry into his hall. The deep dwellers have additional customs regarding death. When the wife of a male deep dweller is informed of his death, she will cut off the first joint of her little finger, then honor her husband's memory with a feast. Elves, on the other hand, do not belief in any sort of continued existence after death and refer to it as "the void". They are not necessarily rigid in this view however, and Oromis told Eragon that he must come to his own decision regarding the matter. The Ra'zac slaughter without mercy and are known to eat the flesh of humans. A Shade will also generally kill without remorse, as it is possessed by Spirits. A Shade can only be killed by a stab through the heart, any other grave injury will cause it to dematerialize, but then reappear elsewhere, crueler than ever. One who kills a Shade and lives becomes known as Shadeslayer. Spirits themselves have no known beginning or end and may potentially be immortal.
Battle and Slaughter
In Eldest, Oromis taught Eragon the Twelve Words of Death in the Ancient Language that can be used to quickly and effectively kill, assuming one is capable of overcoming magical defenses. In the Urgal culture, a Death chant is performed prior to entering battle. A group known as the Laughing Dead, soldiers who were bewitched by Galbatorix to feel no pain, can continue fighting well past the limits of ordinary men. They will only die due to either loss of blood, being beheaded, or potentially a direct stab through the heart, as with a Shade.
Immortality and Fortune-Telling
Those who become Dragon Riders gain a sort of immortality, though they are subject to maladies of the flesh and injury through battle, if they escape these, they can endure forever. This is also true for bonded dragons, and other dragon may gain a sort of immortality through Eldunarí. Nasuada, leader of the Varden and King Orik of Surda have stated their agreement with Eragon's decision not rule over Alagaësia should he and Saphira be successful at defeating Galbatorix, as they feel it is not proper for the land to be ruled by one of the Undying.
Death may sometimes be foreseen by a powerful fortune-teller, though specifics will usually be lacking. The death of Brom was foretold in this manner, though it was not known at the time the identity of who would die.
In Other Works
The concept of death is a key element of most great stories. It features heavily in the Harry Potter series and in other popular works. Death is discussed in great length in most religious work and is often a subject of poetry. See Wikipedia's page about death for more about the matter.