I got into reading Jon Ronson on a long-ago recommendation from Shawn Macomber. My takes on previous Ronson books are here and here. Both those are from 2006, which means it's been way too long since I read him. I was not disappointed: Ronson continues to be a wonderful and insightful writer.
His topic here is (generally speaking) various forms of mental disorder, which won't surprise readers of his previous work. How do we sort out people who are genuinely brain-broken from those who just have unconventional beliefs, or even delusional ones? On a more practical note, how do we find those likely to commit violence on others, and what do we do once we find them?
Although Ronson explores all sorts of oddness here—some of it hilarious—his concentration, implied by the title, is psychopathy. Especially the "test": Robert Hare's checklist of items that can be used to score people to see how psychopathetic they are.
Ronson is open-minded, self-deprecating, and pretty honest for a journalist. He develops relationships with his sources/targets, and displays an uncanny ability to get them to open up, even when it's glaringly obvious that they are kind of/extremely nuts.
If you have ever uttered the phrase "inmates running the asylum" as a metaphor, you'll probably be happy to read about the more-or-less real thing here. Scientologists play a role, and Ronson treats them as fairly as possible.
Ronson really doesn't have a thesis to prove, but I found myself a little more convinced that the psychiatric field contains a few good folks trying to do honest work, but also way too many loons, who misdiagnose, over-diagnose, and (above all) overmedicate. (I said the book was hilarious, but the penultimate chapter, "The Avoidable Death of Rebecca Riley", is totally sobering in this regard.)