Ours is the era of everybody’s autobiography. Bookshops groan with misery-lit memoirs — Never Let Me Go, Dysfunction Without Tears — which dilate on anorexia, alcoholism, cruel bereavement. When is a life worth telling? B.S. Johnson, the London-born novelist (and tireless chronicler of himself), put the most revealing sexual details into his autobiographical novels of the 1960s. They might have amounted to mere solipsistic spouting, were the writing not so good.

James Rhodes, a 40-year-old classical musician, was repeatedly raped at his London prep school in the early 1980s. In his memoir, Instrumental, Rhodes tells how he found salvation in music and became one of our leading concert pianists. Written in faux American hip-jive slang (‘fuck-bucket’, ‘I shit you not’), the book is an attempt, among other things, to give the author’s damaged life justification and meaning. Instrumental may be crudely written, hyperbolic and gruelling to read, but Rhodes’s is a life worth telling all right.

Sexual abuse, previously disregarded, is the child protection issue of our time. Rhodes’s rapist, a school boxing coach named Peter Lee, was traced to Margate and charged, but he died of a stroke before he could stand trial. Many others have been wrongly accused. Not long ago, friends of ours were raided by the Metropolitan Police, who impounded laptops and computer storage devices on suspicion of paedophile activity. The couple had neglected to secure their wireless network with a password but still the police needed to make sure that the modem had indeed been ‘compromised’. After eight weeks, the computers came back with no evidence on them of child pornography. In all likelihood a perfect stranger — a man like Peter Lee — had parked his car outside their house and, using a smartphone, hacked into their Wi-Fi system.

It seems extraordinary that no one thought to question the schoolboy Rhodes when he expressed fear at attending boxing classes, or when blood was seen to run down his legs. For five years the appalling assaults continued. Rhodes describes them unflinchingly and with a proper retrospective fury. His former wife tried to prevent publication of Instrumental on the grounds that their 12-year-old autistic son might be ‘psychologically harmed’ by the graphic detail. Last month the Supreme Court lifted the injunction, arguing (among other things) that the book would help other victims of abuse.

Perhaps it will. At my own boarding school in south London called Brightlands (a misnomer for that dark Victorian-era barracks) the predatory abuse of boys was not uncommon. Any one of us caught masturbating or talking after lights out was made to strip in the bathroom at the end of the corridor, where a sports master (it was always a sports master) beat us with a slipper. It was a shaming punishment that filled me (and still fills me) with impotent perplexity; in some unformulated way I understood that the beatings were a sexual outrage. The school was a feeder for Dulwich College.

Rhodes’s school in St John’s Wood was a feeder for the no less privileged Harrow (where, he tells us, he befriended Benedict Cumberbatch). The violence done to him as a six-year-old inevitably cast a shadow over his life. He suffered nervous breakdowns, eating disorders, depression, drug and alcohol abuse; more than once he attempted suicide. Instrumental is an angry book, but most of the anger is directed by Rhodes at himself (‘I’m a bit of an asshole’). Some readers may weary of what he calls his ‘narcissistic’ and ‘whiny’ company.

Having gone through AA’s 12-step alcoholic recovery programme, Rhodes found solace in piano practice, practice, practice. The classical music he champions here is Chopin, Beethoven, Mozart. Great moderns such as Ligeti, Webern or Messiaen are nowhere to be found. The music’s fuddy-duddy image is of concern to Rhodes. Keen to appear right-on, he describes his favourite composers in strenuously street-cred terms. Chopin was immersed in a ‘dysfunctional, fucked-up turd of a relationship’ with George Sand; Liszt was a ‘wanker’ (news to me).

During piano recitals, Rhodes wears sneakers and jeans like a younger Nigel Kennedy. For all I care he can wear a gold lamé jockstrap, so long as the music’s tip-top. Rhodes is a brilliant concert pianist but anyone who dares to suggest that he might be a teensy bit self-righteous in wishing to ‘save’ classical music (the Daily Telegraph’s ‘douchebag’ music critic Michael White, for example) is aggressively taken down a peg. Editor: where were you?

The legal action taken against Instrumental was probably ill-judged, but I feel sympathy for Rhodes’s ex-wife. Their child has Asperger Syndrome. Living with a teenage autistic son may involve levels of domestic violence, weight-gain from anti-psychotic medications, threats of suicide, school refusal, the destruction of all you hold dear in a family and marriage. Cruelly, an autistic tendency will often transmit itself down the generations like an unwanted gene. (Rhodes himself has Asperger Syndrome.) It would be naive to think that a child with autism might not be traumatised by reading a book like this. Still, the pianist’s life had been well worth telling.