A harrowing account of travels 2,000-miles by riverboat deep into Zaire, along roughly the route depicted in Conrad's fictional Heart of Darkness. Written in the 1980s, it's an observant and disturbing portrait of what is now the Democratic Republic of the Congo. A journalist by trade, Winternitz writes as much about Mobutu and the political chaos she encountersd as the marvels of the tropical rain forest.  (CAF28, $14.00)