For Jon Ronson, journalism is about offering a fair hearing to people who might not otherwise get, or even deserve, it. Over the course of his eight books he’s done this to Ku Klux Klansmen, anthrax hoaxers, cult leaders, paedophiles and people who tweeted insensitive things (the latter, needless to say, caused more controversy than the others). 2011’s The Psychopath Test adds Broadmoor inmates, Haitian death squad leaders, out-of-control experimental psychiatrists, job-slashing CEOs, Scientologists and self-declared messiahs to his rogue’s gallery, but it also reflects on what this kind of writing means to the wider world. Ronson has often found himself ahead of the zeitgeist – Them: Adventures With Extremists tackled Islamic fundamentalism just a few months before 9/11 – and The Psychopath Test confronts this directly. What does it mean to live in a world where, to use Ronson’s terrific phrase, people are “defined by their maddest edges”? On the one hand, you get the DSM, the Bible of psychiatric treatment, which has ballooned from an initial slim list of debilitating mental illnesses to an enormous Behemoth that seems to have a clinical diagnosis for every single human activity. And yet the belief that we’re all in some way dysfunctional hasn’t made us more compassionate. In one of the book’s most chilling chapters he interviews a former reality TV agent, who discloses that information about guests’ medication was used to work out whether they’d make entertaining telly: no pills equals boring guest, anti-psychotic drugs are too risky, but Prozac is just right. Ronson ends that chapter by expressing relief that he’d never been that callous, then – in one of the self-critical pivots the book excels at – spends the next chapter detailing how he added to the media circus surrounding the MI5 whistleblower David Shayler. The Psychopath Test isn’t just a mea culpa, though. Even as Ronson is dissecting his own addiction to the fringe and the unstable, he spins fantastic stories about psychiatrists trying to treat psychopaths through “naked crotch eyeballing sessions” (it’s as bizarre as it sounds) and Tony, a man who faked madness to escape a prison sentence, then found his sentence extended when it was decided by doctors that pretending you’re mad is exactly the sort of thing a mad person would do. It’s a real-life Catch-22 story, which probably explains why Jay Roach has optioned the book for a movie, with Scarlett Johansson starring.