I agree, ?!, with the additional criterion that the oyster has to taste good. Why I can’t read Grisham, or Paretsky, or Clancy, or King, or Rowling, or any number of other skilled plotters who just can’t write, and 98% of current SF. Why I end up re-reading Leonard (or Chandler or Hammett or Bester of Hoban) when I feel an urge for oysters.