Adam Hochschild's "King Leopold's Ghost: A Story of Greed, Terror, and Heroism in Colonial Africa," which will appear in paperback this month, achieves a basic tenet of historical writing: the retrieval of a buried past. Hochschild describes how between 1884 and 1907 Leopold, frantic to carve for himself a colonial empire, lay claim to the Congo under the most paradoxical of guises -- humanitarianism -- while actually letting loose a system of terror in which entire Congolese villages were forced to harvest rubber or face death by their Belgian overseers.