"The question of what should be permitted to go into his diary and what kept forever shrouded goes to the heart of all his writing."
Coetzee's Youth is the second volume of his memoirs. Like Boyhood, it is written in the third person and in the present tense.
There is a gap between the two books, of several years. There is also a gap in the implicit relationship between the author and the main character of each book, if you will: Coetzee seems to ironize his youthful self (about 19 to 24 years old) more than he does his childhood self (up to about 15 years old?).
Even so, this being a memoir, there are still moments, as in Boyhood, in which the adult author seems to be commenting on his development as a writer. Here, near the beginning of Youth, the main character (only later identified as "John") has written about his affair with an older woman in his diary—specifically, about how discouraging he finds the whole relationship to be. When his lover reads his diary, she leaves him, of course, and he wonders about what one should write and what one should not write.
If this is a comment on Coetzee's own fiction, it's hard to say exactly what claim is being made about that fiction; after all, when we read his books, all we have is what they contain and not what he has "forever shrouded." In his books about novelists (The Master of Petersburg and Elizabeth Costello), though, this point might be touched on (as in the passage quoted at the end of my third post on The Master of Petersburg).
Perhaps what I am slowly getting at as I comment on JMC's memoirs is how the two books undermine one's hope that they will provide a reliable "portrait of the artist as a young man." In fact, my edition of Boyhood has a quotation from Michiko Kakutani on the cover: "Fiercely revealing, bluntly unsentimental ... a telling portrait of the artist as a young man that illuminates the hidden source of his art." Every time I read that, it seems like she could have written it without even having read the book: it's such a cliché about memoir writing.
Revelation and unsentimentality are themes in JMC's memoirs; that is, the idea of revelation and the idea of an unsentimental approach to oneself are circled around, but revelation and a "bluntly unsentimental" approach are not the tools JMC is simply "using" here.