This is from page 160 of the Gollancz "SF Masterworks" edition (2011) of Christopher Priest's slipstream (or at any rate elusive) novel The Affirmation (1981).
In an alternate reality (later explored further in the short story collection The Dream Archipelago (2009), which I haven't read yet), one character is asking another to explain some elements of his fictional autobiography, set in our reality (which of course is alternate to theirs):
"Who is Felicity?" [She is a character in the part of the novel set in our reality.]
"What are the Beatles?"
"Where is Manchester, Sheffield, Piraeus?"
"What is England, and which island is it on?"
"Who is Gracia, and why has she [...]?" [Slight spoiler deleted. Gracia is another character.]
"Who was Hitler, what war are you talking about, which cities had they bombed?"
"Who is Alice Dowden?"
"Why was Kennedy assassinated?"
"When were the sixties, what is marijuana, what is a psychedelic rock?"
"You've mentioned London again ... I thought it was a state of mind?"
"Why do you keep talking about Gracia?"
"What happened at Watergate?"
Well, who is Alice Dowden?
[If the answer is that she's a character later in the book, don't tell me! I'll get there soon enough.]
Incidentally, if you can tell me why Kennedy was assassinated, that would also be cool.