And if you wanted to know how not to present a Q and A discussion relating to such a book, you had to be at the Royal Court on Friday afternoon when Gaskill was engaged in conversation by Dominic Cooke, his current successor in the post of artistic director of the English Stage Company.
It was a stumbling affair due to the simple fact that the two of them had obviously not sat down for half an hour beforehand to map out the territory of the conversation.
Cooke said that he had read the book, and enjoyed it. And, at the one point where he put Gaskill on the spot, he gently chided him for not naming names when differing with other directors.
But he was wrong to do so: Gaskill takes up cudgels against Peter Hall for his mask work and verse-speaking edicts, against Jonathan Miller for ignoring the fairytale aspect of The Tempest, against Stephen Daldry for playing "muzak" throughout An Inspector Calls, and clearly against Trevor Nunn for producing classic plays as a sort of poor man's musical. Personally, I think Gaskill's out of order on at least four of those charges.
The point about Gaskill, though, is not these personal animosities, which are slyly and graciously stated in the book, but his tremendous and forbidding sense of integrity about values of text and speech in the theatre, and his unique aesthetic austerity.
Like many at the Court in the early days, he was marked for life by the visit of the Berliner Ensemble to the Palace Theatre in 1956, the year of Brecht's death; and the year of the formation of the ESC, John Osborne's Look Back In Anger and the Suez Crisis.
It was the aesthetics, more than the politics, of the Ensemble that impressed, and he explained to Cooke how the Royal Court gradually developed its own style as a result, mainly through the designs of Jocelyn Herbert.
He told a wonderful story to illustrate his view that few directors, especially foreign ones, honour the intentions of a playwright. The first night of his production of Edward Bond's Saved was attended by many dramaturgs and intendants from Germany. In the interval, one of them was heard to say: "Praise the Lord, there is still work to be done: they have just produced the text, that is all."
Gaskill is a great director, and a great teacher, partly because he doesn't think the director is all that important: "Writers and actors are," he said, "and a director mediates between the two."
He talked a lot about speech and speaking, in a beautiful clear voice, tinged with his native Yorkshire vowels. Dominic Cooke, in sharp contast, mumbled very badly, and his articulation was lazy and slapdash.
"I spend a lot of time teaching actors how to speak," Gaskill said, crossly. ""Actors should know how to speak and how to read the play. Very few do nowadays."
Cooke asked him about young actors doing the classics today. Gaskill refused, contemptuously, to answer this question. It was clear he thought very little of how the classics, or indeed Shakespeare, are done today by young actors or indeed anyone else.
His exemplars, as actors, remain John Gielgud, Edith Evans and Maggie Smith (he rhapsodised, too briefly, about Smith's God-given timing).
And he recalled Lindsay Anderson directing Gielgud and Ralph Richardson in David Storey's Home, coaxing them gently through the play and allowing them to find their way, encouraging them, not really directing at all. "You saw the play coming alive in rehearsal. Of course, it was magical, brilliant directing."
Read his book for more of the same, the different impacts of Brecht and Beckett on our modern theatre, where to place the stress in the main speeches of Hamlet, a brilliant explanation of the Noh Theatre, various ways of producing Macbeth, the importance of punctuation and phrasing in Congreve and Pinter...and much, much more, all wrapped up in easy-to-read, stylish prose in 160 pages. Essential stuff.