4 ideas
In a society where a nightly pill reassigns every citizen to a new home, job and spouse, a man and a woman who happen to be paired for one day decide they want to be together again the next day. The novel follows their attempt to get around the system that is designed to make every pairing last only one day, so that their wish to repeat becomes a plot against the social order.
If homes, jobs and partners are randomly redistributed every day, no one can accumulate wealth, status or advantage, so the hierarchy that comes from entrenchment disappears. The same mechanism also removes the continuity that a self is built from. A person who owns no history, no role and no relationship becomes interchangeable, so perfect equality is paid for with individuality.
When novelty is guaranteed and endless, attraction and pleasure are cheap because every day brings someone new. What marks love is wanting the same person again. Commitment is the deliberate choice of repetition over variety, and it shows only in a world that makes repetition impossible.
Look at which ordinary desire a system is built to prevent, because that desire becomes its central form of rebellion. In a society organized around constant reassignment, the dangerous act is staying the same: keeping a memory, a bond or a place. Seen this way, conservatism and attachment can be radical, depending on what the order requires people to give up.