Flamenco is generally see in two modes: old school and new. If the old style is your thing, Juan Martin's books are as good as any. If you prefer nuevo flamenco, I highly recommend Harmonizing Flamenco From The Guitar Vol.1 by Claude Worms, which contains a catalogue of falstetas by the likes of Paco de Lucia, Rafael Riqueni, Oscar Herrero, Manolo Sanlucar, Vicente Amigo, and others.
My flamenco playing is poor, as I don't use nails. Nevertheless, I just love studying how those guys do what they do, which increases my listening appreciation.