The novel's epigraph and the ending sing the same tune. Take a look at the last two paragraphs of the book:
He fell in October, 1918, on a day that was so quiet and still on the whole front, that the army report confined itself to the single sentence: All quiet on the Western Front.
He had fallen forward and lay on the earth as though sleeping. Turning him over one saw that he could not have suffered long; his face had an expression of calm, as though almost glad the end had come.
We detect a bit of irony in the way that Paul dies on a quiet day, a day when there isn't much action anywhere else on the Front. By the end of the novel, we've witnessed the hellish bombardments Paul has survived in which bullets, shells, and gas surround him like a swarm of bees. The fact that he dies on a relatively peaceful day suggests to us that he either welcomed death, or that he was so unused to calm that he had grown too accustomed to violence to know what to do in a quiet setting. The "expression of calm" on his face makes us feel like he had found his peace in the end. How tragic that fighting on the Front was so horrific that Paul is relieved to die.
The question on our minds, however, is who narrates this last paragraph? Until this point, Paul has narrated the entire novel. So who could be speaking now? All of Paul's best friends have died. Perhaps the speaker is another soldier who discovered Paul's body ends the tale? And who was sensitive enough to look at his face and see that calm? Was it that obvious? And did this person find Paul's account of the war and choose to finish it for him? So many questions.