"The vampire underworld is much larger than most people could imagine. It exists in all the cities mentioned in the book, but also in many, many more. Teenagers, especially, seem to like to act out vampire fantasies"

This quote by James Patterson recommends that the vampire underworld is much bigger than many people believe. It is not limited to the cities discussed in the book, however is present in many more. Teenagers, in specific, seem to be drawn to the concept of vampires and typically act out their fantasies. This could be due to the allure of the mystical and dark nature of vampires, along with the concept of immortality and power that they represent. It is likely that the vampire underworld is far more extensive than we can envision, which it is a popular topic among teenagers.