Fitz-James O'Brien's "Enigma," the progenitor of all invisible monsters, has thrilled readers for a century and a half and inspired several generations of science fiction and horror writers. A masterpiece of mystery, this strange text leaves the reader as perplexed as its befuddled narrator. Is it the exciting account of triumph over evil it purports to be? Or is there more to this than meets the eye? Could it be a subtle attack on slavery in America? Or a defence of the powerless and disenfranchised? Are we dealing with a creature from another planet, a monster of the id, or the...