I spent sixteen years working as a psychiatric nurse, and this is the best on screen portrayal of antisocial personality disorder (i.e. a psychopath/sociopath) I've ever seen. He's easy to get on with, can affect a certain vulnerability, he's sort of nerdishly charming (not necessarily one of the criteria, but it all helps), very calculating, clearly incapable of remorse or empathy, and only allows himself to be in situations in which he has complete control. He also avoids responsibility by rationalising his behaviour. In short, he's one of cinema's most credible villains. His presence in a film where nothing much actually happens (as opposed to, say, a slasher) makes for a genuinely unsettling experience. And yes, avoid the remake.