Guyana, Suriname, and French Guiana are among the least-known places in South America: nine hundred miles of muddy coastline giving way to a forest so dense that even today there are virtually no roads through it; a string of rickety coastal towns situated between the mouths of the Orinoco and Amazon Rivers, where living is so difficult that as many Guianese live abroad as in their homelands; an interior of watery, green anarchy where border disputes...