A friend who studies psychology recommended this book to me knowing that I've long fostered an interest in psychology. For me, therefore, the book was perfect - having no academic grounding in psychology, I would probably struggle with an academic paper on psychopaths, but I found this book to be very well pitched to the masses. It was as light and accessible as a book with such a serious and delicate subject matter could be.
I have always been fascinated by psychopathy and psychological illness more generally, and it really catered to that interest, with original and intriguing material - a real page turner, which I find is rare in books with a 'heavy' subject. However, even if psychology isn't really your bag, Ronson's style and approach makes it a compelling read, and you'll find yourself freaking out your friends and family with 'so unbelievable it has to be true' type stories for ages.
My only criticism is that I suppose I would have liked him to delve a little deeper, analyse a little more - he frequently touches on the question of whether psychopathy, and other mental illnesses, are simply labels thrust by society onto individuals who don't fit the mould, but he never seems to say anything very solid on the matter. I'd also have liked to have read more case studies of less 'extreme' psychopaths - he seems to go for fairly high profile ones, but claims (I think) that 1/100 people are now considered psychopathic, and I assume (hope!) not all of these are homicidal rapists!
Despite these criticisms, I realise that the book is intended to be a 'popular' read, not an in depth analysis of psychopaths, and indeed Ronson makes it clear that he is in no position to provide such an analysis. This in mind, the book is really fantastic, and I'd recommend it to just about anyone.