Good Morning, Mr Mandela by Zelda la Grange – review

Nelson Mandela was a master of the art of political gesture, particularly when it came to racial reconciliation in South Africa. He wore the Springbok captain's jersey at the Rugby World Cup in 1995, he invited his former oppressors to tea, and he made a point of selecting a young Afrikaner as his personal secretary. Her name was Zelda la Grange: she was 23 when he discovered her working as a junior typist in his presidential office, and she would become his manager, his gatekeeper, his confidante and the person to whom he was perhaps closest, after his wife Graça Machel.

He brought her into the inner chambers of South Africa's new power elite, on to the glittering stage of his global travels, and into the sphere of his own fractious family. The consequences were not always happy, not least for La Grange herself, who uses this memoir to settle some scores, to tell her side of the story, and – most poignantly – to begin the process of finding herself now that she has been severed from the relationship that defined her: "I gave him my youth, and perhaps my future too," she writes, stating repeatedly that her commitment to him made it impossible for her to sustain any other relationship: "I couldn't be with a man for 20 minutes without Madiba calling on me to do something."

She understands Mandela, quite simply, as her saviour, and the book feels truest at the beginning, as we witness the awakening of a dull, unconscious racist into a passionate New South African. She wins Mandela over, it seems, with her tears when he addresses her in Afrikaans on their first meeting: they are the tears of shame, and more white South Africans should shed them.

She describes him as a beloved grandfather, but there is an undeniably romantic charge to the relationship: they were in many ways a couple, one governed by rigid gender roles. It was, she writes, a "co-dependency" – "my need to please fitted with his need for absolute loyalty" – and it worked while he ran the show. But as he declined into a lengthy dotage, in a way that has never really been admitted before now, the partnership fell apart. By charting this disintegration, Good Morning, Mr Mandela does not deliver on the chipper, redemptive promise of its title and opening pages, but in fact offers something more valuable, if more distressing: a chronicle of the decline of "the world's most famous man", as the author herself calls him, and thus a reassertion of his mortality.

La Grange is neither a native English speaker nor a writer. Her memoir's artlessness is sometimes its charm, sometimes its impediment: it can be repetitive and self-exculpatory, and overly stuffed with the celebrity-filled logs of interminable world travel. These accounts nonetheless serve unwitting historical purpose in the way they reveal not only their author's ingenuousness, but an aspect of Mandela's own character: how besotted he was with wealth, glamour and particularly royalty. Pages fly past in the company of Naomi Campbell, Prince Albert of Monaco, Bono and Prince Bandar bin Sultan, and gaudy South African tycoons such as Douw Steyn and Sol Kerzner. These, it appears, are Mandela's inner circle, along with some more impressive candidates such as Bill Clinton and Morgan Freeman. La Grange's sole criterion for judging all the above, including Muammar Gaddafi (whom she likes), is whether they treat Mandela well. Here she replicates her boss's own moral blind spot: people were good if they were good to him – which meant supporting his exemplary legacy foundations, certainly, but also hosting him and keeping his grandchildren in bling.

Mandela was a man of probity and did not die wealthy. But, in the manner of a patriarch, he was more than willing to use his name to leverage favours. La Grange betrays both herself and her boss – but does history the service of humanising him – when she tells the story of how the Pondo king demanded Mandela find bursaries for his daughters in the United States. He makes the call, the princesses get their educations, and La Grange's only judgment is that these women have "made us all proud".

Elsewhere, she grapples with the continued anger of black youth. South Africa has changed, she insists: she is the "living proof". Such solipsism, the product of having been Mandela's poster-girl for transformation, contradicts her own acute and empathetic observations, elsewhere in the book, of the poverty that still bedevils black South Africans.

There should be no question about La Grange's commitment and efficiency. But her book demonstrates that she had neither the wisdom nor the authority to manage Mandela once he was no longer able to manage himself. As she puts it: "The older he became and the less able to express his own wishes, the more people were going to move in and get him to do what they wanted." La Grange believes she might have prevented this, had she been allowed. But although she had come to consider herself part of the Mandela family, she was ejected in the end, having to sneak in through back doors to say her goodbyes to the dying man and – outrageously – denied accreditation to attend his burial. In this she was, as in all things, the creation of her maker: he used her to create the barrier he needed from his grasping progeny, and so they dispensed with her as soon as his dotage meant she lost his protection.

Mandela's favourite lines of poetry were from William Henley's "Invictus": "I am the master of my fate / I am the captain of my soul." Little wonder that his was not a gentle decline: he was often angry and distressed, and always wanted to be elsewhere. The account of this is heartbreaking. He carried, obsessively, an empty wallet with nothing but Machel's business card inside it. La Grange accompanied him to at least 20 bookshops to buy the same Collins dictionary, just because he wanted to get out; but because he was not just any old senile shopper his surprise visits would inevitably cause a mayhem that deepened his confusion, and he would have to be whisked away.

To make matters worse, terrible feuds broke out within his large and complicated family, and La Grange claims that his discomfort was exacerbated by this. She offers strong descriptions of the way Machel – whom she champions – was mistreated by Mandela's children, but her loyalty to Mandela's legacy prevents her from giving details that might help us make better sense of what is already in the public domain: that two daughters tried unsuccessfully to replace his appointed trustees with themselves; that a grandson dug up the bones of Mandela's dead children and removed them to his own piece of land, thus precipitating an ugly court battle as Mandela lay dying himself.

Still, even without the detail, the portrait painted here is a devastating and undignified one, as family and friends, courtiers and comrades, struggle to manage the impossible situation of an immortal's impending death while trying to get a bit of the action too. The book ends, as it must, with Mandela's funeral, about which La Grange is excoriating: why, when it had been anticipated for so long, was it so badly managed?

The answer is one that La Grange, by now unmoored and embittered, cannot fully comprehend, because she is so invested: there were too many competing interests around Mandela, and without his own commanding presence to orchestrate them, things fell apart. As they do with the death of a patriarch.

• Mark Gevisser's latest book is Dispatcher: Lost and Found in Johannesburg (Granta). To order Good Morning, Mr Mandela for £15 (RRP £20), go to bookshop.theguardian.com or call 0330 333 6846.