Sat 23 Apr 2011 00.06 BST
The vengeful side of Castle's work first came to public attention through "Desperately Seeking Susan", her essay published in the London Review of Books in March 2005, just a few months after Susan Sontag's death. Here, Castle detailed her "on-again, off-again semi-friendship" with the great woman in which she played the humble groupie to Sontag's imperious star. She served as Sontag's chauffeur around southern California, a sympathetic audience for her kvetching about academics, an eager player in her games of intellectual one-upmanship, a purveyor of lesbian gossip to her closeted but insatiably curious androgynous persona ("I've loved men, Terry, I've loved women").
Eventually, Castle became disillusioned with her role as a generally adoring and dazzled acolyte. "Sontag was a great comic character," she observes. "Dickens or Flaubert or James would have had a field day with her. The carefully cultivated moral seriousness – strenuousness might be a better word – coexisted with a fantastical, Mrs Jellyby-like absurdity." Her deadpan account of Sontag demonstrating how one evades sniper fire in Sarajevo, by ducking in and out of doorways on "Palo Alto's twee, boutique-crammed main drag" in her "intellectual-diva kit", became the prize tidbit at international academic dinner-parties. Castle also vividly describes being Sontag's guest at a dinner of the haute intelligentsia in Manhattan, where she was patronised and ignored, and another fiasco in which she wants to show Sontag off to her partner Blakey or vice-versa, and is snubbed and humiliated.