Luxury has been, in many periods of history, defined by ostentation. In today's world of hyper-visibility, however, privacy has become the ultimate luxury. For the ultra-wealthy, privacy can involve not only confidentiality and concealment but also outright seclusion. Even the desire to belong, which seems untangleable from visibility, can be sated quietly, through exclusive communities, members-only clubs and networks all but invisible to outsiders. Taken together, these books suggest that true wealth isn't measured by what it displays, but by what it manages to hide.