He did a TV programme based on it, was shown on BBC in the 1990s. Norman likes to be a bit of an iconoclast, but I think he's correct quite a lot of the time, a lot of the "great" conductors were showmen who cultivated their mystique more than they served the music. Things are different now.... the authentic/historically informed performance movement has forced conductors to have more respect for the score and the composers' intentions, and the way to achieve this is through rigorous musicianship.
One of the interesting points in the TV programme was Leonard Slatkin, at that time newly-appointed chief of the BBC SO, revealing that he had refused to take his fees on occasions where he felt he hadn't been good enough.