So you think the fillings in your teeth are receiving clandestine radio signals from the World Bank. What to do? First, see your doctor. Second, start studying New York author Arthur Goldwag’s smart new compendium of all things cloaked and covert, Cults, Conspiracies, and Secret Societies: The Straight Scoop on Freemasons, the Illuminati, Skull and Bones, Black Helicopters, the New World Order, and Many, Many More (Vintage, $19.95). With clever little essays on everything from the Order of the Solar Temple to the Symbionese Liberation Army, Goldwag has created a book that’s hard to stop reading—the equivalent of eating a bowl of peanuts (with the accent on nuts). By the end, you have a clear image of the “thought contagion” that sometimes causes people to lose the plot so completely that they have to make one up.