The outsider here is Adele. She grows up in Liverpool, the doted-on daughter of a small-time criminal.
When her father kills himself, her mother says Adele has to start earning her keep and her options narrow d down to a job on a department store perfume counter or finding a rich husband.
However, Adele feels she is better than the women around her. She manages by dint of a little creative lying to get herself a place at a northern university and becomes an observer of the social experiment that seems to be going on, never quite caught up in the political radicalism or hippy nonsense happening around her, but there to witness it all.
This ugly modern university, based on York where Grant studied, is a place with no rules.
Students are encouraged to question and rebel. If they want to dress in outlandish clothes, meditate the days away or blow their mind with drugs, no one stops them.
Inevitably, all are changed and not everyone survives.
The story is centred on Adele's group of friends - glamorous and fragile couple Evie and Stevie, earnest musician Gillian, flamboyant gay Bobby, stridently political Rose - and it pivots on a single, tragic event that continues to haunt them through their lives as they try to find someone to blame for it.
In Upstairs at the Party the era and people are painted vividly; all except Adele, who never becomes more than a commentator on events and an analyser of situations.
At times, even the other characters criticise her for being hard, distant, primitive or unreconstructed, but that seems a bit of a get-out for Grant - an excuse for having a character who appears so curiously uninvolved in her own life.
Still, Adele is a merciless observer: alert to every detail, questioning and cynical. She is rarely tripped up by sentimentality or nostalgia.
This is a bold piece of writing about youth - about how we create ourselves and how we hurt ourselves.
And how quickly we find that we are no longer young at all.
It is, as Adele admits, "a rush through life" and, although the later chapters don't have the same resonance as the university days, there's a mystery to solve that re-shapes the past.
Upstairs at the Party is essentially a gloomy story but it's brought to life so colourfully and expressively that it's a hugely compelling read.