Another one of the great scifi stories by Greg Egan - he is really incredible rich in transcribing ideas of new physics into a story in/of the future, trying out the thoughts in fictional reality.
This time the story starts out far in the future where uploading, backup, nanotechnology - and therefore basic immortality - have all come true, only distances remain far as the speed of light is still a limit. During some test of the fundamental physical laws a new stable state of the universe is created which spreads with half-lightspeed ... Several twists and turns let us see our part of the world as the strange and degenerated quantum world whereas the 'novo-vacuum' is in fact a much richer quantum superposition.
Interesting is here that though this plays in a distant future with unbelievable progress in technology, people are still people with similar problems as today - can this be true?
Also the picture of the development of oneself - a continously changing entity with some feeling of continuity - as a vector parallel transport (which is the Schild's Ladder in the book) is quite fascinating - so staying oneself (parallel vector) but the outcome of the process depends on the path the vector has gone through.
It was the kind of behavior that could only occur when people had been trapped for thousands of years staring at the same sights, fetishising everything around them, spiralling down towards the fullblown insanity of religion. You didn't need gates and barbed wire to make a prison. Familiarity could pin you to the ground far more efficiently.