When Vladimir Nabokov died in 1977, he left instructions for his heirs to burn the 138 handwritten index cards that made up the rough draft of his final and unfinished novel, The Original of Laura. But Nabokov’s wife, Vera, could not bear to destroy her husband’s last work, and when she died, the fate of the manuscript fell to her son. Dmitri Nabokov, now seventy-five--the Russian novelist’s on...