The wikipedia entry on the rebel is a good place to start.
Starting in 'media res' - in the middle of things is a literary technique which subverts the idea that a story should have a beginning, it also invokes the feeling that we are in the middle of things without knowing what is going on, and we must spend effort to discover this, that is establish coherence. One might think oif here of Heideggers notion of throwness, that is being thrown into the world.
The absurd is one reaction when the world loses meaning. There is a well-known theatre of the absurd which takes off from Camus work.
As you point out, Camus work is over 60 years old; to get a grasp of what he is saying one has to immerse oneself or at least have a nodding acquaintance of the intellectual currents and preoccupations of that time. And one of those themes is taking the Nietszchean 'Death of God' seriously by the intellectual elite - which probably given serious impetus after two devastating world wars (which was also what propelled the absurdism of the dadaist avant-garde art group). What could be more absurd than the trench warfare of the first world war, the use of men as cannon-fodder? Of course this intellectual climate is normative now (I don't mean absurdism here but athiesm).
Camus points out the idea of the absurd cannot be possibly self-consistent, for even if one declares that one lacks faith in the world, or has lost belief in any transcendental meanings, one retains belief in oneself and in ones own perceptions, feelings and intellects. This then allows the beginning of an intellectual current - existentialism - as propounded by Sartre. (Even if Kierkegaard, the Nordic philosopher who predated him and was resiliently a Christian is seen by some as its founder of existentialism - perhaps because he grasped we must live as though God did not exist).
Following on from Nietszches 'Death of God', Camus points out that the French revolutionaries (the rebels) killed 'God' too. That is they killed the French king, who embodied the divine right of Kings. That Marxists tried to kill history (another divine agency - think of fate or karma) by bringing utopian values into the world.
The death and resurrection of gods, according to some histories of myths, is an old and reoccuring story; one might think Nietszche slayed God, only for others to resurrect it as economic-political theologies which assumed transcendental values, ie Marxism & Capitalism.