Published two weeks after his seventieth birthday, Ada, or Ardor is one of Nabokov's greatest masterpieces, the glorious culmination of his career as a novelist.  It tells a love story troubled by incest.  But more: it is also at once a fairy tale, epic, philosophical treatise on the nature of time, parody of the history of the novel, and erotic catalogue.   Ada, or Ardor is no less than the supreme work of an imagination at white heat. This is the first American edition to include the extensive and ingeniously  sardonic appendix by the author, written under the anagrammatic pseudonym Vivian Darkbloom.