If the book doesn't interest me and it is required reading I'd want to know what I am required to know and just get that out of the book using superreading and dipping. I'd be looking for the overview, plot characters, setting. Then maybe go deeper and find the theme, symbolism, philosophy, language and imagery.
I'd do 3 maybe 5 - 20 minute activation sessions and mind mapping. I'd consider rapid reading if I developed an interest in the book and wanted to know more.
I would have the advantage of having pulled this information out of the book by repeated views, rather than trying to remember it all from only one rapid read.
I'd fall straight into a rapid read if the book was for pleasure and I wanted to devote some time to it without the need to remember much of it later.
Alex