Why are we drawn to books about terrible and disturbing true events? Are our motives always wholesome? Certainly my family are doubtful about my small library of books on the Holocaust. “You wouldn’t read a book about Fred West,” they say.

I make the case that so much of the story of the Nazi years contains clear warnings for today, many of which are ignored every day by apparently decent and responsible people. What, though, when the story is of one abused and humiliated person? A child such as Kevin Lewis, whose autobiographical account of dreadful childhood abuse, The Kid, became a bestseller in 2003; or Dave Pelzer, author of A Child Called It, which swept to international success in 1995? Is it just prurience that leads us to their stories, a sort of horrified schadenfreude? (Euan Ferguson wrote in the Observer in 2001 of Dave Pelzer’s “pornography of misery”.) Or is there a broader and more wholesome impulse at work?

Kevin Lewis himself admits in his latest book: “I have thought a great deal about why so many people want to read a story like mine.” There are, he suggests, two reasons. “One must be that they have endured some sort of similar experience, or at least know someone else who has, and the other must be that they are trying to find out what happens in a world that they can’t imagine, because their childhoods were as happy as they should have been.”

In other words, it’s a mixture of emotional need and a hint of prurient curiosity, which seems about right.

But why are the books written? Writers write, we are always told, to please no one but themselves. In Moving On, Kevin Lewis tells us that he wrote The Kid as a personal cleansing exercise, with no thought of publication. He found the process of showing the book to his wife and to publishers emotionally disturbing. This latest book, you feel, is a continuation of the process of leaving the past behind. He describes piloting his manuscript to publication in a way that’s interesting, but may also be about mentally tidying up the whole affair.

Richard B Pelzer’s book tells of another sort of moving on. The author is the younger brother of Dave Pelzer, for one thing: the very same Richard who joined in the dreadful abuse of the “child called It”, kept in a basement at the instigation of their mother. Here he tells us about that time, explaining, all too clearly, how his own terror and powerlessness forced him to find someone further down the pecking order (and what an old story that is). “The sorrow on his face told me I had made him feel just as I wanted him to. The same way I felt at school.”

It’s a relentless tale, with little sense of redemption; a tale of heartless, alcohol-fuelled cruelty on a scale that, argues Richard Pelzer, couldn’t happen now. “Given the amount of awareness now present in our schools, we as a community would not allow it to happen.”

He’s probably right. And yet Kevin Lewis’s book tells us that even after the publication of The Kid, he discovered that his abusive mother was beating her grandchildren. Communication and bureaucracy in public services are, in his opinion, still faulty, and still letting children down. Break a bottle over someone’s head in the pub, he says, and you’re in trouble. Hit your child in the same way, and you’ll probably get away with it.

“It seems to me from my own experience, the experience of my nephews and nieces, and from the letters I receive, that the more vulnerable a person is, whether it be a child, a disabled person or an old age pensioner, the harder it is to have their abusers convicted of their crimes,” he writes.

Perhaps that’s the most important lesson: that the powerlessness of those most vulnerable, which spurs some people to violence, also protects the perpetrators. Come to think of it, that was one of the lessons of the Holocaust too.