The Pure Gold Baby, By Margaret Drabble, Canongate Books

Through one mother-daughter bond, this novel traces the journey of a generation

"She would be what she would be – a millstone, an everlasting burden, a pure gold baby, a precious cargo". In Margaret Drabble's superb new novel, a richly complex narrative voice achieves a choric magnificence hardly equalled in her earlier work. The Pure Gold Baby considers, with saturnalian humour and elegiac sorrow, how far the author's generation has come, along "that bright curve that led us on to the future. The radiant way."

At the story's centre stands a mother-child diptych, a secular pietà, reprising but reconfiguring familiar motifs. Like Rosamund in The Millstone (1965), a young professional woman – in this case an anthropologist, Jess – becomes pregnant, struggling with the demands of single motherhood. The baby is "pure gold", not despite but because of her developmental difficulties. Anna will never leave home; never read or write. Her life has no plot. She lives within the moment, an indwelling presence in the novel, which writes itself around her.

The narrator, Eleanor, is Jess's close friend. As they approach old age, she has privately elected to write the intimate story of Jess and Anna. She is "I" – but sometimes also "we": "We worried for her, we, her friends, her generation, her fellow-mothers". She directs her observations to or at "you", the reader. Although the narrator is an eyewitness, her perspective is full of holes: iffy assumptions, confabulations, misinterpretations, secrets Jess has chosen not to share.

What Eleanor has to tell is a love story, but primarily neither eros nor agape. Love is understood in two senses, as mother-love and as friendship between mothers: "Jess has given the large part of her life to exclusive and unconditional and necessary love. That is her story, which I have presumptuously taken it upon myself to attempt to tell."

Warts and all, Eleanor might have added. We are aware of the narrator's shortcomings as well as Jess's, and Katie's and Maroussia's: what George Eliot might have called their "spots of commonness". They are representatives of a disputatious female intelligentsia who have stumbled through every mistake of their generation. The story is told in loops and swerves, recapitulating, prefiguring.

There are passages of amazing emotional power, expressive of the narrator's passionate protectiveness: the novel extends its wings over Anna. In a moving opening section, Jess is shown in her first field trip to Africa, before Anna's advent, responding to the sight of children with the disease "then popularly known as Lobster Claw syndrome". This awoke in Jess what seems to the narrator a proleptic "tender spirit of response... The maternal spirit had brooded on the still and distant waters of that great and shining lake."

But the narrative voice doesn't hold back. It has learnt from Jess a deadpan anthropological lingo to denote the curious tribal behaviour of its own North London community. Like any friend, Eleanor has her cruel insights. She notes Jess's self-deceit as she consigns the pure gold baby to a special needs school. Whose needs? "Anna is a lucky girl," goes the refrain. Really? We fear for Anna and the story's ironies stealthily build up that apprehension, for Anna – like all the novel's children – is at the mercy of flawed and cloven human nature, which offers at best "good enough" mothering.

The Sixties generation "tried to look through the doors of perception. We thought there was something to see, on the other side." Lunatic social experiments confound themselves in laugh-aloud humour. The funniest and saddest scenes expose the imbecilities practised in "therapeutic communities": "This is the continent of Dr Nicholls... We are in his protectorate."

The Pure Gold Baby thinks profoundly on living in time, where, as we look back from the closing season of our lives, "all seems fore-ordained and fore-suffered and yet all is unfinished and unknown".

The novel reflects on how to live well. We don't really know. We do our best. It isn't good enough. It's all we have.