I'm currently reading "Sins of the Brother". It's (according to the subtitle) the "Definitive story of Ivan Milat and the backpacker murders".
Now I don't know if you've seen Wolf Creek, but I have and it was scary. Not so much the horror of the film, that isn't it, it's more the thought that these things really did and have happened.
I'm only just getting into Part two of the book, which within the first 2 chapters has already gotten in to the 'guts' of what that man's life was like. Part one was more about his childhood, his family life, and the lives of his family.
I think what I'm more frightened of is the fact that someone thought it was ok to do this to people. Not what they did, but that they thought it was ok. I mean, what they did was horrific, but that someone thought this was a fair thing to do to another living human being.... and to think up doing these sorts of things in the first place... well.
Have to admit, it's a good bedtime read though. I like reading biographies and autobiographies most of all, and this one is quite thorough in it's telling.