The narrator, Meursault, speaking of course in 1st person, is hardly what is called a 'reliable narrator,' and is a far cry from an omniscient narrator (one who knows everything in the story and explains it). Meursault explains nothing. We basically live in his mind and see the world through his eyes. So, the language in the book are the thoughts, words and perceptions of Meursault, our Absurdist narrator. His speech correlates well with the style of the narration. His speech is direct and indifferent. He simply states things like "mother died today or maybe it was yesterday" in his characteristic stoic way. When questioned about the murder he committed, he talks about the heat and the sun and how the sun drove him to it. The reader is at the mercy of his perspective which tends only to focus on what is immediately present: the prison cell itself, because it is immediately present to him, is more interesting than why he's in there in the first place. (later in the novel, however, he will dwell on his fate; and this is the point where the other characters and the enforcement of law collide with Meursault's place in the world. They try to establish order and meaning whereas Meursault feels like a stranger in that world, hence the title.
Nothing, not even religion, offers him any hope for Meursault. He dwells on his fate and loss of freedom but finds no solace from any ideology. Meursault's speech and narration are stylistically structured on describing reactions to the immediate environment, not feeling a connection to people and their laws, beliefs, etc. When his mother dies, she is no longer a part of his life and in fact, hadn't been when she was alive. Since she is dead, she is out of sight, out of mind for Meursault. So she does not affect his life. That's why he speaks so dispassionately about her. He feels like a stranger and in the end, this is what gives him peace. That's why his speech and descriptions seem so removed from emotion and the world. Unlike the other characters who follow society, Religion and other philosophical beliefs, Meursault quietly embraces living in a meaningless universe: accepting the "absurdity" of it. The speech and narration reflect this.
Check out The Myth of Sisyphus, particularly the closing section, compare Meursault with Sisyphus, Camus' other Absurd hero.