Yes, we have to put up with reading about Ian Curtis' untimely demise and that nightclub somewhere up north again, but the necessary duplication is kept to a minimum.
It's not an official biography, but Bernard interjects corrections occasionally. At the end, we do know more about him, but still not much. He's a private person, who doesn't want fame and doesn't even want to clarify people's misconceptions! Frustrating and confusing.
Luckily, Nolan writes well (if with the occasional amount of repetition) and has interviewed many, many people from Bernard's past and it's this combination of research and good writing that keeps you going through the mystery of Bernard's life.
8/10 - well worth reading.