Wilson Harris's tenth novel, first published in 1972, is set in Edinburgh but, like much of his subsequent work, bridges continents by its imaginative reach. ''Doctor Black Marsden', tramp, shaman, and conjurer, is an ambivalent Merlin-figure representing both the hero's personal (and archetypal) shadow, and the creative, magus-like activity of the author himself.' Michael Gilkes, "Journal of C...