Please don't spoil any details!
There is no way to spoil as we know more or less the 90% of the story John tells, and some of the things in the book are not really what happened but his view, or the interpretation that made the person who wrote the book after the conversation with John.
For example, the "reason" why Terry wasn't on OES is not true, according to Terry. And I'm not telling what the book says, but what the book says is not the truth according to Terry.
I don't intend to read the book for now or at least I don't mind being spoiled so, if spoilers are allowed here, what was the "real" reason why both Terry and Hal left the band?
And also, admitting that John Illsley didn't write the book, why is the book under his name? It's true though that I can't see any mention of the book on John's site.
It could well have been something like : "My life in Dire Straits" by XXX with the help of John Illsely so I don't quite get it here 
About Terry, I mentioned in a previous post.
About Hal, is too surreal to explain without reading.
Biographies are usually not written by the person, are usually made through a conversatio and the writer takes notes and record it to then type it into what would be the book. It's not like writing really but transcribing the notes and recordings, and that sometimes leds to write things that are not exactly what the person said, as usually what is written has to follow a "style" that can be readable. Who does that usually works for the book company who publish it.
Also, the person usually takes a read to correct mistakes. That didn't happen this time, so there are mistakes in the book and also some things written in a way that John doesn't like, but it was too late to correct.