William Gass' wonderful introduction to Penguin's reissue of William Gaddis' "The Recognitions" (excerpted March 28) and his droll observations about being consistently mistaken for Gaddis himself put me in mind of a similar and amusing anecdote involving Don DeLillo. This story was told to me by Elisabeth Sifton, DeLillo's editor at Viking for "White Noise" and also Gaddis's editor there for "Carpenter's Gothic." It seems that DeLillo was in attendance at a literary cocktail party when a woman came up to him and said, "I know you. I know who you are. I've read all your books, Mister Gaddis !" DeLillo, without missing a beat, replied, "I'm sorry. You've made a mistake. I'm not William Gaddis, I'm Thomas Pynchon."