Obviously, being an unauthorised biography, there is only so much that Myles Palmer could do in terms of research, so it's fair to say that he's done a very good job with the tools available. Most comments that are unsubstantiated are stated as such, and hearsay is usually clearly noted. It's a pity Knopfler chose not to assist, as he's painted in a positive light on the whole - goodness knows why he couldn't make some sort of contribution.
Bear in mind that this is now relatively out of date, and therefore misses the latter parts of his career.