An old Russian proverb holds that sometimes the best lie is the truth. How better to test that subversive notion than by examining the life stories told by a famous novelist  one of those professionals whose trade, it may be said, is to lie for a living? Set your story in South Africa, where governments are not just economical with the truth but downright miserly, and the stakes are even higher.

Absolution, the first novel by Patrick Flanery, is likely to disturb anyone with settled views on South Africa. In part a literary detective story, it is a deeply unsentimental portrait of a society where freedom came recently and a lot of people are not entirely sure whether to embrace, ban or shoot it.

Clare Wald is a celebrated novelist who lives comfortably in Cape Town, until the night her house is invaded by a mysterious gang who want neither her money nor her life but a piece of her past. Later on, when a young academic, Sam Leroux, returns to Cape Town after years abroad with a commission to write the biography of the reclusive novelist, he is after something similar. Leroux is not quite what he seems, but then the stories Wald spins are not reliable either, and a dangerous duel takes place between the older writer and her young inquisitor. He is her confessor, there to hear her sins. The question is whether he can ever absolve her of crimes, real and imagined.

Among the ghosts who haunt Wald is her father, a good judge in the apartheid years, whose liberal ideals she failed to match and whose wig turns up in unlikely places, a reminder of her shortcomings. There is her daughter, Laura, who backed violent resistance against the apartheid state and paid with her life. There is her sister, also murdered, but in her case for supporting the old regime. Both deaths now seem to the old woman increasingly senseless, and she is convinced that she is somehow to blame.

Absolution is a book of questions about what is right and who is pure. Might a liberal writer such as Wald have flirted with the censors who banned her work? Was the truth and reconciliation commission more than a carillon of high-sounding clichés, a theatre that showcased the exuberant cruelty of those who ran the apartheid machine but did little to assuage the sufferings of its victims? In a nice doubling of ironies, Wald is writing her version of how she came to betray herself, and others, in a work she calls Absolution, while at the same time her life is being recorded by Leroux. In one of the dramatic surprises Flanery does so well, it turns out that Leroux is closer to Wald for reasons each finds too painful to face.

Flanery has set Absolution in the years before and after South Africa's first free election in 1994, when white nationalists ceded power to black nationalists, who seem to grow, uncannily, more like the regime they have replaced. One of the constant strengths of this novel is the way it faces the violence of everyday life and the unpalatable reality that, nearly two decades after the coming of democracy, while party functionaries fatten themselves, the poor riot in the townships for a better life and the rich lock themselves behind suburban walls and electric fences.

Perhaps it helps that Flanery is an American; it gives him distance and a different take on things. His South Africa is familiar, yet slightly, strangely, off-key. His portrait of Cape Town in its eerie sedateness is very good, even if Johannesburg eludes him. But where it counts he gets it right.

Wald's dilemma is how to face her failings and stand up for what she has written. Writers of all stripes have a history of provoking South African regimes, all the way back to the very first settlements. The apartheid government took words into state ownership, perverted the meaning of some and forbade the use of others. And many people accepted this as normal in a country that had gone off its head.

But then as another American writer, Allen Drury, remarked nearly 50 years ago, after travelling through the country in a state of perpetual astonishment, South Africa is "a very strange society". His book of that title was banned by the masters of apartheid. With censorship now likely to make a comeback under the current government, what writers do becomes increasingly important. And a novel like Absolution is timely.

 Christopher Hope's Shooting Angels is published by Atlantic.

Early in this compelling debut, Clare Wald, an ageing famous writer, is talking to a younger man at her house in South Africa's Western Cape: "You look fashionable," she says dismissively. Flanery describes how "she draws her lips back on the final syllable, her teeth part. There's a flicker of grey tongue."

This mixture of restrained dialogue and faintly disturbing observation is typical. Wald is addressing Sam Leroux, her recently appointed biographer, who has returned to his native South Africa to work on the book. After a home-invasion by masked gunmen, Wald has moved to a compound in an exclusive neighbourhood with a high wall and "barbed wire shaped and painted to mimic trained ivy".

Wald's life has been deeply embroiled in the events and upheavals of apartheid and post-apartheid South Africa. Her daughter, Laura, a "journalist until she became wholly invested in the armed struggle", disappeared, while her sister Nora was murdered. As the book unfolds, and Leroux's own connection to Wald is revealed, we are forced to consider and then reconsider Clare's role in these events.

The novel has four, often contradictory narrative strands: "Sam" is told from Leroux's perspective; "Clare" charts Wald's internal attempts to make sense of her daughter's disappearance; "Absolution" relates events in the third person; while "1989" begins at the point the lives of a young Leroux and Laura Wald first intersect.

Although the mystery of Laura's disappearance provides much of the dramatic tension, Wald is the novel's crowning achievement. Cantankerous and complex in a convincing way, she is prone to pithy pronouncements: "We all know how people suffer over the unexpected violent death of a family member  It's vivisection  It's limb loss."

At times Flanery's prose evokes Graham Greene; but Wald's search for profundity can feel a little contrived.

A literary thriller whose writing is consistently first class, Absolution might have been even better if it's structure had been more straightforward. Opinions will differ as to whether the strands of the plot are braided or merely knotted together, since, at the end, several questions remain unanswered.