It must be around thirty years since I first (and last) read Non-Stop. There are still lots of things to like about it. It was a deliberate response to the Heinlein stories later published as Orphans of the Sky, taking the concept of people living on a generation starship, but who do not realise their real situation, to a new level. Where Heinlein's protagonists were barely aware that they were on a spaceship at all, Aldiss's know that they are on a long journey but very little else, and the fact that they have partial knowledge allows Aldiss to partially misdirect us so that the eventual conceptual breakthrough is all the more dramatic.
The gender perspective of the book is a little regrettable. The book starts with an argument between Roy Complain, the protagonist, and his lover; their relationship is pretty abusive, and when she is kidnapped we never hear of her again. We do a little better with Roy's other lover, Vyann, who he first encounters as a security official from a more socially advanced group. I feel she rather loses agency as their relationship prospers and Roy gets to save her once of twice, but she does get the last word in the book:
‘Now they'll have no alternative but to take us back to Earth,' Vyann said in a tiny voice. She looked at Complain; she tried, woman-like, to guess at all the new interests that awaited them. She tried to guess at the exquisite pressures which would attend the adjustment of every ship-dweller to the sublimities of Earth. It was as if everyone was about to be born, she thought, smiling into Complain's awakened face. He was her sort; neither of them had ever been really sure of what they wanted: so they would be most likely to find it.Though that "woman-like" is rather jarring.
I was surprised to realise that there is quite a strong decolonisation metaphor at the core of the story. Complain and his fellow inhabitants of the ship turn out to have been denied agency by the rest of humanity, treated as subhumans - smaller, smellier and with much shorter lifespans - and in his climactic debate with Complain, the Earth agent Fermour actually invokes Albert Schweitzer as a good example. The ensuing conflict changed Complain's world forever, and while it may not necessarily be for the better, it is from a position of superior understanding.
A final thought, on religion: the belief system of the starship turns out to be a set of completely invented and manipulated lies, but the priest Marapper is sincere. He also appears to die and return to life.
Non-Stop kicks off my reread of the BSFA, Clarke and Tiptree winners because it was given a retrospective award by the BSFA in 2008 as the best book of 1958. It beat The Big Time by Fritz Leiber, Have Spacesuit Will Travel by Heinlein, A Case Of Conscience and A Clash of Cymbals/The Triumph of Time by James Blish and Who? by Algis Budrys. I have read all but the last if these and I reckon the BSFA got it right. (I don't recall voting myself.) I loved both the Leiber and Heinlein when I was younger, and A Case Of Conscience is trying to say something very earnestly, but Non-Stop, the first of Aldiss's many novels, is really breaking new ground and establishing a fresh way of doing things. It has dated but was worth going back to.