Invisible City by Julia Dahl Minotaur Books, $24.99, 298 pages, ISBN 978-1-250-04339-9 Have you ever thought about any of the subcultures which exist in the midst of what we call ‘normal’ or regular society? Religious groups like the Amish, Mennonites, Hare Krishna’s, Islamist’s, Mormons, Sikhs and Hindus are all stitched into the fabric of America in plain sight . . . yet remain secretive and mostly unknown by all