It is surprising how loath film-makers have been to make films about themselves, or about the magic medium of illusion they transmit to the world. As egotistical and narcissistic as most film artists are—including the writers and directors, who are the crucial creators, of course—they have seldom dared turn their cameras on their own involuted lives or explore the cultural importance and impermanence of most of the work they do. For that reason, Sunset Boulevard … was not only rare as a...